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android_kernel_motorola_sm6225/kernel/sched.c
Greg Banks e16b38f713 [PATCH] cpumask: export cpu_online_map and cpu_possible_map consistently 
cpumask: ensure that the cpu_online_map and cpu_possible_map bitmasks, and
hence all the macros in <linux/cpumask.h> that require them, are available to
modules for all supported combinations of architecture and CONFIG_SMP.

Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-02 07:57:17 -07:00

6929 lines
173 KiB
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/*
* kernel/sched.c
*
* Kernel scheduler and related syscalls
*
* Copyright (C) 1991-2002 Linus Torvalds
*
* 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and
* make semaphores SMP safe
* 1998-11-19 Implemented schedule_timeout() and related stuff
* by Andrea Arcangeli
* 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar:
* hybrid priority-list and round-robin design with
* an array-switch method of distributing timeslices
* and per-CPU runqueues. Cleanups and useful suggestions
* by Davide Libenzi, preemptible kernel bits by Robert Love.
* 2003-09-03 Interactivity tuning by Con Kolivas.
* 2004-04-02 Scheduler domains code by Nick Piggin
*/
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/debug_locks.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/suspend.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <linux/tsacct_kern.h>
#include <linux/kprobes.h>
#include <linux/delayacct.h>
#include <asm/tlb.h>
#include <asm/unistd.h>
/*
* Convert user-nice values [ -20 ... 0 ... 19 ]
* to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
* and back.
*/
#define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20)
#define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20)
#define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
/*
* 'User priority' is the nice value converted to something we
* can work with better when scaling various scheduler parameters,
* it's a [ 0 ... 39 ] range.
*/
#define USER_PRIO(p) ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
/*
* Some helpers for converting nanosecond timing to jiffy resolution
*/
#define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
#define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
/*
* These are the 'tuning knobs' of the scheduler:
*
* Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
* default timeslice is 100 msecs, maximum timeslice is 800 msecs.
* Timeslices get refilled after they expire.
*/
#define MIN_TIMESLICE max(5 * HZ / 1000, 1)
#define DEF_TIMESLICE (100 * HZ / 1000)
#define ON_RUNQUEUE_WEIGHT 30
#define CHILD_PENALTY 95
#define PARENT_PENALTY 100
#define EXIT_WEIGHT 3
#define PRIO_BONUS_RATIO 25
#define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
#define INTERACTIVE_DELTA 2
#define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
#define STARVATION_LIMIT (MAX_SLEEP_AVG)
#define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
/*
* If a task is 'interactive' then we reinsert it in the active
* array after it has expired its current timeslice. (it will not
* continue to run immediately, it will still roundrobin with
* other interactive tasks.)
*
* This part scales the interactivity limit depending on niceness.
*
* We scale it linearly, offset by the INTERACTIVE_DELTA delta.
* Here are a few examples of different nice levels:
*
* TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
* TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
* TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
*
* (the X axis represents the possible -5 ... 0 ... +5 dynamic
* priority range a task can explore, a value of '1' means the
* task is rated interactive.)
*
* Ie. nice +19 tasks can never get 'interactive' enough to be
* reinserted into the active array. And only heavily CPU-hog nice -20
* tasks will be expired. Default nice 0 tasks are somewhere between,
* it takes some effort for them to get interactive, but it's not
* too hard.
*/
#define CURRENT_BONUS(p) \
(NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
MAX_SLEEP_AVG)
#define GRANULARITY (10 * HZ / 1000 ? : 1)
#ifdef CONFIG_SMP
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
num_online_cpus())
#else
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
#endif
#define SCALE(v1,v1_max,v2_max) \
(v1) * (v2_max) / (v1_max)
#define DELTA(p) \
(SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
INTERACTIVE_DELTA)
#define TASK_INTERACTIVE(p) \
((p)->prio <= (p)->static_prio - DELTA(p))
#define INTERACTIVE_SLEEP(p) \
(JIFFIES_TO_NS(MAX_SLEEP_AVG * \
(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
#define TASK_PREEMPTS_CURR(p, rq) \
((p)->prio < (rq)->curr->prio)
/*
* task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
* to time slice values: [800ms ... 100ms ... 5ms]
*
* The higher a thread's priority, the bigger timeslices
* it gets during one round of execution. But even the lowest
* priority thread gets MIN_TIMESLICE worth of execution time.
*/
#define SCALE_PRIO(x, prio) \
max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
static unsigned int static_prio_timeslice(int static_prio)
{
if (static_prio < NICE_TO_PRIO(0))
return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio);
else
return SCALE_PRIO(DEF_TIMESLICE, static_prio);
}
static inline unsigned int task_timeslice(struct task_struct *p)
{
return static_prio_timeslice(p->static_prio);
}
/*
* These are the runqueue data structures:
*/
struct prio_array {
unsigned int nr_active;
DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */
struct list_head queue[MAX_PRIO];
};
/*
* This is the main, per-CPU runqueue data structure.
*
* Locking rule: those places that want to lock multiple runqueues
* (such as the load balancing or the thread migration code), lock
* acquire operations must be ordered by ascending &runqueue.
*/
struct rq {
spinlock_t lock;
/*
* nr_running and cpu_load should be in the same cacheline because
* remote CPUs use both these fields when doing load calculation.
*/
unsigned long nr_running;
unsigned long raw_weighted_load;
#ifdef CONFIG_SMP
unsigned long cpu_load[3];
#endif
unsigned long long nr_switches;
/*
* This is part of a global counter where only the total sum
* over all CPUs matters. A task can increase this counter on
* one CPU and if it got migrated afterwards it may decrease
* it on another CPU. Always updated under the runqueue lock:
*/
unsigned long nr_uninterruptible;
unsigned long expired_timestamp;
unsigned long long timestamp_last_tick;
struct task_struct *curr, *idle;
struct mm_struct *prev_mm;
struct prio_array *active, *expired, arrays[2];
int best_expired_prio;
atomic_t nr_iowait;
#ifdef CONFIG_SMP
struct sched_domain *sd;
/* For active balancing */
int active_balance;
int push_cpu;
int cpu; /* cpu of this runqueue */
struct task_struct *migration_thread;
struct list_head migration_queue;
#endif
#ifdef CONFIG_SCHEDSTATS
/* latency stats */
struct sched_info rq_sched_info;
/* sys_sched_yield() stats */
unsigned long yld_exp_empty;
unsigned long yld_act_empty;
unsigned long yld_both_empty;
unsigned long yld_cnt;
/* schedule() stats */
unsigned long sched_switch;
unsigned long sched_cnt;
unsigned long sched_goidle;
/* try_to_wake_up() stats */
unsigned long ttwu_cnt;
unsigned long ttwu_local;
#endif
struct lock_class_key rq_lock_key;
};
static DEFINE_PER_CPU(struct rq, runqueues);
static inline int cpu_of(struct rq *rq)
{
#ifdef CONFIG_SMP
return rq->cpu;
#else
return 0;
#endif
}
/*
* The domain tree (rq->sd) is protected by RCU's quiescent state transition.
* See detach_destroy_domains: synchronize_sched for details.
*
* The domain tree of any CPU may only be accessed from within
* preempt-disabled sections.
*/
#define for_each_domain(cpu, __sd) \
for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() (&__get_cpu_var(runqueues))
#define task_rq(p) cpu_rq(task_cpu(p))
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
#endif
#ifndef finish_arch_switch
# define finish_arch_switch(prev) do { } while (0)
#endif
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(struct rq *rq, struct task_struct *p)
{
return rq->curr == p;
}
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq->lock.owner = current;
#endif
/*
* If we are tracking spinlock dependencies then we have to
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
spin_unlock_irq(&rq->lock);
}
#else /* __ARCH_WANT_UNLOCKED_CTXSW */
static inline int task_running(struct rq *rq, struct task_struct *p)
{
#ifdef CONFIG_SMP
return p->oncpu;
#else
return rq->curr == p;
#endif
}
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
#ifdef CONFIG_SMP
/*
* We can optimise this out completely for !SMP, because the
* SMP rebalancing from interrupt is the only thing that cares
* here.
*/
next->oncpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
spin_unlock_irq(&rq->lock);
#else
spin_unlock(&rq->lock);
#endif
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_SMP
/*
* After ->oncpu is cleared, the task can be moved to a different CPU.
* We must ensure this doesn't happen until the switch is completely
* finished.
*/
smp_wmb();
prev->oncpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
#endif
}
#endif /* __ARCH_WANT_UNLOCKED_CTXSW */
/*
* __task_rq_lock - lock the runqueue a given task resides on.
* Must be called interrupts disabled.
*/
static inline struct rq *__task_rq_lock(struct task_struct *p)
__acquires(rq->lock)
{
struct rq *rq;
repeat_lock_task:
rq = task_rq(p);
spin_lock(&rq->lock);
if (unlikely(rq != task_rq(p))) {
spin_unlock(&rq->lock);
goto repeat_lock_task;
}
return rq;
}
/*
* task_rq_lock - lock the runqueue a given task resides on and disable
* interrupts. Note the ordering: we can safely lookup the task_rq without
* explicitly disabling preemption.
*/
static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
__acquires(rq->lock)
{
struct rq *rq;
repeat_lock_task:
local_irq_save(*flags);
rq = task_rq(p);
spin_lock(&rq->lock);
if (unlikely(rq != task_rq(p))) {
spin_unlock_irqrestore(&rq->lock, *flags);
goto repeat_lock_task;
}
return rq;
}
static inline void __task_rq_unlock(struct rq *rq)
__releases(rq->lock)
{
spin_unlock(&rq->lock);
}
static inline void task_rq_unlock(struct rq *rq, unsigned long *flags)
__releases(rq->lock)
{
spin_unlock_irqrestore(&rq->lock, *flags);
}
#ifdef CONFIG_SCHEDSTATS
/*
* bump this up when changing the output format or the meaning of an existing
* format, so that tools can adapt (or abort)
*/
#define SCHEDSTAT_VERSION 12
static int show_schedstat(struct seq_file *seq, void *v)
{
int cpu;
seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
seq_printf(seq, "timestamp %lu\n", jiffies);
for_each_online_cpu(cpu) {
struct rq *rq = cpu_rq(cpu);
#ifdef CONFIG_SMP
struct sched_domain *sd;
int dcnt = 0;
#endif
/* runqueue-specific stats */
seq_printf(seq,
"cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
cpu, rq->yld_both_empty,
rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt,
rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
rq->ttwu_cnt, rq->ttwu_local,
rq->rq_sched_info.cpu_time,
rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);
seq_printf(seq, "\n");
#ifdef CONFIG_SMP
/* domain-specific stats */
preempt_disable();
for_each_domain(cpu, sd) {
enum idle_type itype;
char mask_str[NR_CPUS];
cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
seq_printf(seq, "domain%d %s", dcnt++, mask_str);
for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
itype++) {
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu",
sd->lb_cnt[itype],
sd->lb_balanced[itype],
sd->lb_failed[itype],
sd->lb_imbalance[itype],
sd->lb_gained[itype],
sd->lb_hot_gained[itype],
sd->lb_nobusyq[itype],
sd->lb_nobusyg[itype]);
}
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance);
}
preempt_enable();
#endif
}
return 0;
}
static int schedstat_open(struct inode *inode, struct file *file)
{
unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
char *buf = kmalloc(size, GFP_KERNEL);
struct seq_file *m;
int res;
if (!buf)
return -ENOMEM;
res = single_open(file, show_schedstat, NULL);
if (!res) {
m = file->private_data;
m->buf = buf;
m->size = size;
} else
kfree(buf);
return res;
}
struct file_operations proc_schedstat_operations = {
.open = schedstat_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/*
* Expects runqueue lock to be held for atomicity of update
*/
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{
if (rq) {
rq->rq_sched_info.run_delay += delta_jiffies;
rq->rq_sched_info.pcnt++;
}
}
/*
* Expects runqueue lock to be held for atomicity of update
*/
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{
if (rq)
rq->rq_sched_info.cpu_time += delta_jiffies;
}
# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
#else /* !CONFIG_SCHEDSTATS */
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{}
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{}
# define schedstat_inc(rq, field) do { } while (0)
# define schedstat_add(rq, field, amt) do { } while (0)
#endif
/*
* rq_lock - lock a given runqueue and disable interrupts.
*/
static inline struct rq *this_rq_lock(void)
__acquires(rq->lock)
{
struct rq *rq;
local_irq_disable();
rq = this_rq();
spin_lock(&rq->lock);
return rq;
}
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
/*
* Called when a process is dequeued from the active array and given
* the cpu. We should note that with the exception of interactive
* tasks, the expired queue will become the active queue after the active
* queue is empty, without explicitly dequeuing and requeuing tasks in the
* expired queue. (Interactive tasks may be requeued directly to the
* active queue, thus delaying tasks in the expired queue from running;
* see scheduler_tick()).
*
* This function is only called from sched_info_arrive(), rather than
* dequeue_task(). Even though a task may be queued and dequeued multiple
* times as it is shuffled about, we're really interested in knowing how
* long it was from the *first* time it was queued to the time that it
* finally hit a cpu.
*/
static inline void sched_info_dequeued(struct task_struct *t)
{
t->sched_info.last_queued = 0;
}
/*
* Called when a task finally hits the cpu. We can now calculate how
* long it was waiting to run. We also note when it began so that we
* can keep stats on how long its timeslice is.
*/
static void sched_info_arrive(struct task_struct *t)
{
unsigned long now = jiffies, delta_jiffies = 0;
if (t->sched_info.last_queued)
delta_jiffies = now - t->sched_info.last_queued;
sched_info_dequeued(t);
t->sched_info.run_delay += delta_jiffies;
t->sched_info.last_arrival = now;
t->sched_info.pcnt++;
rq_sched_info_arrive(task_rq(t), delta_jiffies);
}
/*
* Called when a process is queued into either the active or expired
* array. The time is noted and later used to determine how long we
* had to wait for us to reach the cpu. Since the expired queue will
* become the active queue after active queue is empty, without dequeuing
* and requeuing any tasks, we are interested in queuing to either. It
* is unusual but not impossible for tasks to be dequeued and immediately
* requeued in the same or another array: this can happen in sched_yield(),
* set_user_nice(), and even load_balance() as it moves tasks from runqueue
* to runqueue.
*
* This function is only called from enqueue_task(), but also only updates
* the timestamp if it is already not set. It's assumed that
* sched_info_dequeued() will clear that stamp when appropriate.
*/
static inline void sched_info_queued(struct task_struct *t)
{
if (unlikely(sched_info_on()))
if (!t->sched_info.last_queued)
t->sched_info.last_queued = jiffies;
}
/*
* Called when a process ceases being the active-running process, either
* voluntarily or involuntarily. Now we can calculate how long we ran.
*/
static inline void sched_info_depart(struct task_struct *t)
{
unsigned long delta_jiffies = jiffies - t->sched_info.last_arrival;
t->sched_info.cpu_time += delta_jiffies;
rq_sched_info_depart(task_rq(t), delta_jiffies);
}
/*
* Called when tasks are switched involuntarily due, typically, to expiring
* their time slice. (This may also be called when switching to or from
* the idle task.) We are only called when prev != next.
*/
static inline void
__sched_info_switch(struct task_struct *prev, struct task_struct *next)
{
struct rq *rq = task_rq(prev);
/*
* prev now departs the cpu. It's not interesting to record
* stats about how efficient we were at scheduling the idle
* process, however.
*/
if (prev != rq->idle)
sched_info_depart(prev);
if (next != rq->idle)
sched_info_arrive(next);
}
static inline void
sched_info_switch(struct task_struct *prev, struct task_struct *next)
{
if (unlikely(sched_info_on()))
__sched_info_switch(prev, next);
}
#else
#define sched_info_queued(t) do { } while (0)
#define sched_info_switch(t, next) do { } while (0)
#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */
/*
* Adding/removing a task to/from a priority array:
*/
static void dequeue_task(struct task_struct *p, struct prio_array *array)
{
array->nr_active--;
list_del(&p->run_list);
if (list_empty(array->queue + p->prio))
__clear_bit(p->prio, array->bitmap);
}
static void enqueue_task(struct task_struct *p, struct prio_array *array)
{
sched_info_queued(p);
list_add_tail(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* Put task to the end of the run list without the overhead of dequeue
* followed by enqueue.
*/
static void requeue_task(struct task_struct *p, struct prio_array *array)
{
list_move_tail(&p->run_list, array->queue + p->prio);
}
static inline void
enqueue_task_head(struct task_struct *p, struct prio_array *array)
{
list_add(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* __normal_prio - return the priority that is based on the static
* priority but is modified by bonuses/penalties.
*
* We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
* into the -5 ... 0 ... +5 bonus/penalty range.
*
* We use 25% of the full 0...39 priority range so that:
*
* 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
* 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
*
* Both properties are important to certain workloads.
*/
static inline int __normal_prio(struct task_struct *p)
{
int bonus, prio;
bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
prio = p->static_prio - bonus;
if (prio < MAX_RT_PRIO)
prio = MAX_RT_PRIO;
if (prio > MAX_PRIO-1)
prio = MAX_PRIO-1;
return prio;
}
/*
* To aid in avoiding the subversion of "niceness" due to uneven distribution
* of tasks with abnormal "nice" values across CPUs the contribution that
* each task makes to its run queue's load is weighted according to its
* scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
* scaled version of the new time slice allocation that they receive on time
* slice expiry etc.
*/
/*
* Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
* If static_prio_timeslice() is ever changed to break this assumption then
* this code will need modification
*/
#define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
#define LOAD_WEIGHT(lp) \
(((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
#define PRIO_TO_LOAD_WEIGHT(prio) \
LOAD_WEIGHT(static_prio_timeslice(prio))
#define RTPRIO_TO_LOAD_WEIGHT(rp) \
(PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))
static void set_load_weight(struct task_struct *p)
{
if (has_rt_policy(p)) {
#ifdef CONFIG_SMP
if (p == task_rq(p)->migration_thread)
/*
* The migration thread does the actual balancing.
* Giving its load any weight will skew balancing
* adversely.
*/
p->load_weight = 0;
else
#endif
p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority);
} else
p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio);
}
static inline void
inc_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
rq->raw_weighted_load += p->load_weight;
}
static inline void
dec_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
rq->raw_weighted_load -= p->load_weight;
}
static inline void inc_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running++;
inc_raw_weighted_load(rq, p);
}
static inline void dec_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running--;
dec_raw_weighted_load(rq, p);
}
/*
* Calculate the expected normal priority: i.e. priority
* without taking RT-inheritance into account. Might be
* boosted by interactivity modifiers. Changes upon fork,
* setprio syscalls, and whenever the interactivity
* estimator recalculates.
*/
static inline int normal_prio(struct task_struct *p)
{
int prio;
if (has_rt_policy(p))
prio = MAX_RT_PRIO-1 - p->rt_priority;
else
prio = __normal_prio(p);
return prio;
}
/*
* Calculate the current priority, i.e. the priority
* taken into account by the scheduler. This value might
* be boosted by RT tasks, or might be boosted by
* interactivity modifiers. Will be RT if the task got
* RT-boosted. If not then it returns p->normal_prio.
*/
static int effective_prio(struct task_struct *p)
{
p->normal_prio = normal_prio(p);
/*
* If we are RT tasks or we were boosted to RT priority,
* keep the priority unchanged. Otherwise, update priority
* to the normal priority:
*/
if (!rt_prio(p->prio))
return p->normal_prio;
return p->prio;
}
/*
* __activate_task - move a task to the runqueue.
*/
static void __activate_task(struct task_struct *p, struct rq *rq)
{
struct prio_array *target = rq->active;
if (batch_task(p))
target = rq->expired;
enqueue_task(p, target);
inc_nr_running(p, rq);
}
/*
* __activate_idle_task - move idle task to the _front_ of runqueue.
*/
static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
{
enqueue_task_head(p, rq->active);
inc_nr_running(p, rq);
}
/*
* Recalculate p->normal_prio and p->prio after having slept,
* updating the sleep-average too:
*/
static int recalc_task_prio(struct task_struct *p, unsigned long long now)
{
/* Caller must always ensure 'now >= p->timestamp' */
unsigned long sleep_time = now - p->timestamp;
if (batch_task(p))
sleep_time = 0;
if (likely(sleep_time > 0)) {
/*
* This ceiling is set to the lowest priority that would allow
* a task to be reinserted into the active array on timeslice
* completion.
*/
unsigned long ceiling = INTERACTIVE_SLEEP(p);
if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
/*
* Prevents user tasks from achieving best priority
* with one single large enough sleep.
*/
p->sleep_avg = ceiling;
/*
* Using INTERACTIVE_SLEEP() as a ceiling places a
* nice(0) task 1ms sleep away from promotion, and
* gives it 700ms to round-robin with no chance of
* being demoted. This is more than generous, so
* mark this sleep as non-interactive to prevent the
* on-runqueue bonus logic from intervening should
* this task not receive cpu immediately.
*/
p->sleep_type = SLEEP_NONINTERACTIVE;
} else {
/*
* Tasks waking from uninterruptible sleep are
* limited in their sleep_avg rise as they
* are likely to be waiting on I/O
*/
if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
if (p->sleep_avg >= ceiling)
sleep_time = 0;
else if (p->sleep_avg + sleep_time >=
ceiling) {
p->sleep_avg = ceiling;
sleep_time = 0;
}
}
/*
* This code gives a bonus to interactive tasks.
*
* The boost works by updating the 'average sleep time'
* value here, based on ->timestamp. The more time a
* task spends sleeping, the higher the average gets -
* and the higher the priority boost gets as well.
*/
p->sleep_avg += sleep_time;
}
if (p->sleep_avg > NS_MAX_SLEEP_AVG)
p->sleep_avg = NS_MAX_SLEEP_AVG;
}
return effective_prio(p);
}
/*
* activate_task - move a task to the runqueue and do priority recalculation
*
* Update all the scheduling statistics stuff. (sleep average
* calculation, priority modifiers, etc.)
*/
static void activate_task(struct task_struct *p, struct rq *rq, int local)
{
unsigned long long now;
now = sched_clock();
#ifdef CONFIG_SMP
if (!local) {
/* Compensate for drifting sched_clock */
struct rq *this_rq = this_rq();
now = (now - this_rq->timestamp_last_tick)
+ rq->timestamp_last_tick;
}
#endif
if (!rt_task(p))
p->prio = recalc_task_prio(p, now);
/*
* This checks to make sure it's not an uninterruptible task
* that is now waking up.
*/
if (p->sleep_type == SLEEP_NORMAL) {
/*
* Tasks which were woken up by interrupts (ie. hw events)
* are most likely of interactive nature. So we give them
* the credit of extending their sleep time to the period
* of time they spend on the runqueue, waiting for execution
* on a CPU, first time around:
*/
if (in_interrupt())
p->sleep_type = SLEEP_INTERRUPTED;
else {
/*
* Normal first-time wakeups get a credit too for
* on-runqueue time, but it will be weighted down:
*/
p->sleep_type = SLEEP_INTERACTIVE;
}
}
p->timestamp = now;
__activate_task(p, rq);
}
/*
* deactivate_task - remove a task from the runqueue.
*/
static void deactivate_task(struct task_struct *p, struct rq *rq)
{
dec_nr_running(p, rq);
dequeue_task(p, p->array);
p->array = NULL;
}
/*
* resched_task - mark a task 'to be rescheduled now'.
*
* On UP this means the setting of the need_resched flag, on SMP it
* might also involve a cross-CPU call to trigger the scheduler on
* the target CPU.
*/
#ifdef CONFIG_SMP
#ifndef tsk_is_polling
#define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
#endif
static void resched_task(struct task_struct *p)
{
int cpu;
assert_spin_locked(&task_rq(p)->lock);
if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED)))
return;
set_tsk_thread_flag(p, TIF_NEED_RESCHED);
cpu = task_cpu(p);
if (cpu == smp_processor_id())
return;
/* NEED_RESCHED must be visible before we test polling */
smp_mb();
if (!tsk_is_polling(p))
smp_send_reschedule(cpu);
}
#else
static inline void resched_task(struct task_struct *p)
{
assert_spin_locked(&task_rq(p)->lock);
set_tsk_need_resched(p);
}
#endif
/**
* task_curr - is this task currently executing on a CPU?
* @p: the task in question.
*/
inline int task_curr(const struct task_struct *p)
{
return cpu_curr(task_cpu(p)) == p;
}
/* Used instead of source_load when we know the type == 0 */
unsigned long weighted_cpuload(const int cpu)
{
return cpu_rq(cpu)->raw_weighted_load;
}
#ifdef CONFIG_SMP
struct migration_req {
struct list_head list;
struct task_struct *task;
int dest_cpu;
struct completion done;
};
/*
* The task's runqueue lock must be held.
* Returns true if you have to wait for migration thread.
*/
static int
migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req)
{
struct rq *rq = task_rq(p);
/*
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
if (!p->array && !task_running(rq, p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
init_completion(&req->done);
req->task = p;
req->dest_cpu = dest_cpu;
list_add(&req->list, &rq->migration_queue);
return 1;
}
/*
* wait_task_inactive - wait for a thread to unschedule.
*
* The caller must ensure that the task *will* unschedule sometime soon,
* else this function might spin for a *long* time. This function can't
* be called with interrupts off, or it may introduce deadlock with
* smp_call_function() if an IPI is sent by the same process we are
* waiting to become inactive.
*/
void wait_task_inactive(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
int preempted;
repeat:
rq = task_rq_lock(p, &flags);
/* Must be off runqueue entirely, not preempted. */
if (unlikely(p->array || task_running(rq, p))) {
/* If it's preempted, we yield. It could be a while. */
preempted = !task_running(rq, p);
task_rq_unlock(rq, &flags);
cpu_relax();
if (preempted)
yield();
goto repeat;
}
task_rq_unlock(rq, &flags);
}
/***
* kick_process - kick a running thread to enter/exit the kernel
* @p: the to-be-kicked thread
*
* Cause a process which is running on another CPU to enter
* kernel-mode, without any delay. (to get signals handled.)
*
* NOTE: this function doesnt have to take the runqueue lock,
* because all it wants to ensure is that the remote task enters
* the kernel. If the IPI races and the task has been migrated
* to another CPU then no harm is done and the purpose has been
* achieved as well.
*/
void kick_process(struct task_struct *p)
{
int cpu;
preempt_disable();
cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
smp_send_reschedule(cpu);
preempt_enable();
}
/*
* Return a low guess at the load of a migration-source cpu weighted
* according to the scheduling class and "nice" value.
*
* We want to under-estimate the load of migration sources, to
* balance conservatively.
*/
static inline unsigned long source_load(int cpu, int type)
{
struct rq *rq = cpu_rq(cpu);
if (type == 0)
return rq->raw_weighted_load;
return min(rq->cpu_load[type-1], rq->raw_weighted_load);
}
/*
* Return a high guess at the load of a migration-target cpu weighted
* according to the scheduling class and "nice" value.
*/
static inline unsigned long target_load(int cpu, int type)
{
struct rq *rq = cpu_rq(cpu);
if (type == 0)
return rq->raw_weighted_load;
return max(rq->cpu_load[type-1], rq->raw_weighted_load);
}
/*
* Return the average load per task on the cpu's run queue
*/
static inline unsigned long cpu_avg_load_per_task(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long n = rq->nr_running;
return n ? rq->raw_weighted_load / n : SCHED_LOAD_SCALE;
}
/*
* find_idlest_group finds and returns the least busy CPU group within the
* domain.
*/
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
{
struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
unsigned long min_load = ULONG_MAX, this_load = 0;
int load_idx = sd->forkexec_idx;
int imbalance = 100 + (sd->imbalance_pct-100)/2;
do {
unsigned long load, avg_load;
int local_group;
int i;
/* Skip over this group if it has no CPUs allowed */
if (!cpus_intersects(group->cpumask, p->cpus_allowed))
goto nextgroup;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
/* Bias balancing toward cpus of our domain */
if (local_group)
load = source_load(i, load_idx);
else
load = target_load(i, load_idx);
avg_load += load;
}
/* Adjust by relative CPU power of the group */
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
if (local_group) {
this_load = avg_load;
this = group;
} else if (avg_load < min_load) {
min_load = avg_load;
idlest = group;
}
nextgroup:
group = group->next;
} while (group != sd->groups);
if (!idlest || 100*this_load < imbalance*min_load)
return NULL;
return idlest;
}
/*
* find_idlest_queue - find the idlest runqueue among the cpus in group.
*/
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
cpumask_t tmp;
unsigned long load, min_load = ULONG_MAX;
int idlest = -1;
int i;
/* Traverse only the allowed CPUs */
cpus_and(tmp, group->cpumask, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
load = weighted_cpuload(i);
if (load < min_load || (load == min_load && i == this_cpu)) {
min_load = load;
idlest = i;
}
}
return idlest;
}
/*
* sched_balance_self: balance the current task (running on cpu) in domains
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
* SD_BALANCE_EXEC.
*
* Balance, ie. select the least loaded group.
*
* Returns the target CPU number, or the same CPU if no balancing is needed.
*
* preempt must be disabled.
*/
static int sched_balance_self(int cpu, int flag)
{
struct task_struct *t = current;
struct sched_domain *tmp, *sd = NULL;
for_each_domain(cpu, tmp) {
/*
* If power savings logic is enabled for a domain, stop there.
*/
if (tmp->flags & SD_POWERSAVINGS_BALANCE)
break;
if (tmp->flags & flag)
sd = tmp;
}
while (sd) {
cpumask_t span;
struct sched_group *group;
int new_cpu;
int weight;
span = sd->span;
group = find_idlest_group(sd, t, cpu);
if (!group)
goto nextlevel;
new_cpu = find_idlest_cpu(group, t, cpu);
if (new_cpu == -1 || new_cpu == cpu)
goto nextlevel;
/* Now try balancing at a lower domain level */
cpu = new_cpu;
nextlevel:
sd = NULL;
weight = cpus_weight(span);
for_each_domain(cpu, tmp) {
if (weight <= cpus_weight(tmp->span))
break;
if (tmp->flags & flag)
sd = tmp;
}
/* while loop will break here if sd == NULL */
}
return cpu;
}
#endif /* CONFIG_SMP */
/*
* wake_idle() will wake a task on an idle cpu if task->cpu is
* not idle and an idle cpu is available. The span of cpus to
* search starts with cpus closest then further out as needed,
* so we always favor a closer, idle cpu.
*
* Returns the CPU we should wake onto.
*/
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, struct task_struct *p)
{
cpumask_t tmp;
struct sched_domain *sd;
int i;
if (idle_cpu(cpu))
return cpu;
for_each_domain(cpu, sd) {
if (sd->flags & SD_WAKE_IDLE) {
cpus_and(tmp, sd->span, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
if (idle_cpu(i))
return i;
}
}
else
break;
}
return cpu;
}
#else
static inline int wake_idle(int cpu, struct task_struct *p)
{
return cpu;
}
#endif
/***
* try_to_wake_up - wake up a thread
* @p: the to-be-woken-up thread
* @state: the mask of task states that can be woken
* @sync: do a synchronous wakeup?
*
* Put it on the run-queue if it's not already there. The "current"
* thread is always on the run-queue (except when the actual
* re-schedule is in progress), and as such you're allowed to do
* the simpler "current->state = TASK_RUNNING" to mark yourself
* runnable without the overhead of this.
*
* returns failure only if the task is already active.
*/
static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
{
int cpu, this_cpu, success = 0;
unsigned long flags;
long old_state;
struct rq *rq;
#ifdef CONFIG_SMP
struct sched_domain *sd, *this_sd = NULL;
unsigned long load, this_load;
int new_cpu;
#endif
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
cpu = task_cpu(p);
this_cpu = smp_processor_id();
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
if (cpu == this_cpu) {
schedstat_inc(rq, ttwu_local);
goto out_set_cpu;
}
for_each_domain(this_cpu, sd) {
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_remote);
this_sd = sd;
break;
}
}
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
/*
* Check for affine wakeup and passive balancing possibilities.
*/
if (this_sd) {
int idx = this_sd->wake_idx;
unsigned int imbalance;
imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
load = source_load(cpu, idx);
this_load = target_load(this_cpu, idx);
new_cpu = this_cpu; /* Wake to this CPU if we can */
if (this_sd->flags & SD_WAKE_AFFINE) {
unsigned long tl = this_load;
unsigned long tl_per_task = cpu_avg_load_per_task(this_cpu);
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
* of the current CPU:
*/
if (sync)
tl -= current->load_weight;
if ((tl <= load &&
tl + target_load(cpu, idx) <= tl_per_task) ||
100*(tl + p->load_weight) <= imbalance*load) {
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and
* there is no bad imbalance.
*/
schedstat_inc(this_sd, ttwu_move_affine);
goto out_set_cpu;
}
}
/*
* Start passive balancing when half the imbalance_pct
* limit is reached.
*/
if (this_sd->flags & SD_WAKE_BALANCE) {
if (imbalance*this_load <= 100*load) {
schedstat_inc(this_sd, ttwu_move_balance);
goto out_set_cpu;
}
}
}
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
out_set_cpu:
new_cpu = wake_idle(new_cpu, p);
if (new_cpu != cpu) {
set_task_cpu(p, new_cpu);
task_rq_unlock(rq, &flags);
/* might preempt at this point */
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
this_cpu = smp_processor_id();
cpu = task_cpu(p);
}
out_activate:
#endif /* CONFIG_SMP */
if (old_state == TASK_UNINTERRUPTIBLE) {
rq->nr_uninterruptible--;
/*
* Tasks on involuntary sleep don't earn
* sleep_avg beyond just interactive state.
*/
p->sleep_type = SLEEP_NONINTERACTIVE;
} else
/*
* Tasks that have marked their sleep as noninteractive get
* woken up with their sleep average not weighted in an
* interactive way.
*/
if (old_state & TASK_NONINTERACTIVE)
p->sleep_type = SLEEP_NONINTERACTIVE;
activate_task(p, rq, cpu == this_cpu);
/*
* Sync wakeups (i.e. those types of wakeups where the waker
* has indicated that it will leave the CPU in short order)
* don't trigger a preemption, if the woken up task will run on
* this cpu. (in this case the 'I will reschedule' promise of
* the waker guarantees that the freshly woken up task is going
* to be considered on this CPU.)
*/
if (!sync || cpu != this_cpu) {
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
success = 1;
out_running:
p->state = TASK_RUNNING;
out:
task_rq_unlock(rq, &flags);
return success;
}
int fastcall wake_up_process(struct task_struct *p)
{
return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
}
EXPORT_SYMBOL(wake_up_process);
int fastcall wake_up_state(struct task_struct *p, unsigned int state)
{
return try_to_wake_up(p, state, 0);
}
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*/
void fastcall sched_fork(struct task_struct *p, int clone_flags)
{
int cpu = get_cpu();
#ifdef CONFIG_SMP
cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
#endif
set_task_cpu(p, cpu);
/*
* We mark the process as running here, but have not actually
* inserted it onto the runqueue yet. This guarantees that
* nobody will actually run it, and a signal or other external
* event cannot wake it up and insert it on the runqueue either.
*/
p->state = TASK_RUNNING;
/*
* Make sure we do not leak PI boosting priority to the child:
*/
p->prio = current->normal_prio;
INIT_LIST_HEAD(&p->run_list);
p->array = NULL;
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (unlikely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
p->oncpu = 0;
#endif
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
#endif
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
* resulting in more scheduling fairness.
*/
local_irq_disable();
p->time_slice = (current->time_slice + 1) >> 1;
/*
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
p->first_time_slice = 1;
current->time_slice >>= 1;
p->timestamp = sched_clock();
if (unlikely(!current->time_slice)) {
/*
* This case is rare, it happens when the parent has only
* a single jiffy left from its timeslice. Taking the
* runqueue lock is not a problem.
*/
current->time_slice = 1;
scheduler_tick();
}
local_irq_enable();
put_cpu();
}
/*
* wake_up_new_task - wake up a newly created task for the first time.
*
* This function will do some initial scheduler statistics housekeeping
* that must be done for every newly created context, then puts the task
* on the runqueue and wakes it.
*/
void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
{
struct rq *rq, *this_rq;
unsigned long flags;
int this_cpu, cpu;
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_RUNNING);
this_cpu = smp_processor_id();
cpu = task_cpu(p);
/*
* We decrease the sleep average of forking parents
* and children as well, to keep max-interactive tasks
* from forking tasks that are max-interactive. The parent
* (current) is done further down, under its lock.
*/
p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
p->prio = effective_prio(p);
if (likely(cpu == this_cpu)) {
if (!(clone_flags & CLONE_VM)) {
/*
* The VM isn't cloned, so we're in a good position to
* do child-runs-first in anticipation of an exec. This
* usually avoids a lot of COW overhead.
*/
if (unlikely(!current->array))
__activate_task(p, rq);
else {
p->prio = current->prio;
p->normal_prio = current->normal_prio;
list_add_tail(&p->run_list, &current->run_list);
p->array = current->array;
p->array->nr_active++;
inc_nr_running(p, rq);
}
set_need_resched();
} else
/* Run child last */
__activate_task(p, rq);
/*
* We skip the following code due to cpu == this_cpu
*
* task_rq_unlock(rq, &flags);
* this_rq = task_rq_lock(current, &flags);
*/
this_rq = rq;
} else {
this_rq = cpu_rq(this_cpu);
/*
* Not the local CPU - must adjust timestamp. This should
* get optimised away in the !CONFIG_SMP case.
*/
p->timestamp = (p->timestamp - this_rq->timestamp_last_tick)
+ rq->timestamp_last_tick;
__activate_task(p, rq);
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
/*
* Parent and child are on different CPUs, now get the
* parent runqueue to update the parent's ->sleep_avg:
*/
task_rq_unlock(rq, &flags);
this_rq = task_rq_lock(current, &flags);
}
current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
task_rq_unlock(this_rq, &flags);
}
/*
* Potentially available exiting-child timeslices are
* retrieved here - this way the parent does not get
* penalized for creating too many threads.
*
* (this cannot be used to 'generate' timeslices
* artificially, because any timeslice recovered here
* was given away by the parent in the first place.)
*/
void fastcall sched_exit(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
/*
* If the child was a (relative-) CPU hog then decrease
* the sleep_avg of the parent as well.
*/
rq = task_rq_lock(p->parent, &flags);
if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
p->parent->time_slice += p->time_slice;
if (unlikely(p->parent->time_slice > task_timeslice(p)))
p->parent->time_slice = task_timeslice(p);
}
if (p->sleep_avg < p->parent->sleep_avg)
p->parent->sleep_avg = p->parent->sleep_avg /
(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
(EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
}
/**
* prepare_task_switch - prepare to switch tasks
* @rq: the runqueue preparing to switch
* @next: the task we are going to switch to.
*
* This is called with the rq lock held and interrupts off. It must
* be paired with a subsequent finish_task_switch after the context
* switch.
*
* prepare_task_switch sets up locking and calls architecture specific
* hooks.
*/
static inline void prepare_task_switch(struct rq *rq, struct task_struct *next)
{
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
}
/**
* finish_task_switch - clean up after a task-switch
* @rq: runqueue associated with task-switch
* @prev: the thread we just switched away from.
*
* finish_task_switch must be called after the context switch, paired
* with a prepare_task_switch call before the context switch.
* finish_task_switch will reconcile locking set up by prepare_task_switch,
* and do any other architecture-specific cleanup actions.
*
* Note that we may have delayed dropping an mm in context_switch(). If
* so, we finish that here outside of the runqueue lock. (Doing it
* with the lock held can cause deadlocks; see schedule() for
* details.)
*/
static inline void finish_task_switch(struct rq *rq, struct task_struct *prev)
__releases(rq->lock)
{
struct mm_struct *mm = rq->prev_mm;
long prev_state;
rq->prev_mm = NULL;
/*
* A task struct has one reference for the use as "current".
* If a task dies, then it sets TASK_DEAD in tsk->state and calls
* schedule one last time. The schedule call will never return, and
* the scheduled task must drop that reference.
* The test for TASK_DEAD must occur while the runqueue locks are
* still held, otherwise prev could be scheduled on another cpu, die
* there before we look at prev->state, and then the reference would
* be dropped twice.
* Manfred Spraul <manfred@colorfullife.com>
*/
prev_state = prev->state;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
if (mm)
mmdrop(mm);
if (unlikely(prev_state == TASK_DEAD)) {
/*
* Remove function-return probe instances associated with this
* task and put them back on the free list.
*/
kprobe_flush_task(prev);
put_task_struct(prev);
}
}
/**
* schedule_tail - first thing a freshly forked thread must call.
* @prev: the thread we just switched away from.
*/
asmlinkage void schedule_tail(struct task_struct *prev)
__releases(rq->lock)
{
struct rq *rq = this_rq();
finish_task_switch(rq, prev);
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
/* In this case, finish_task_switch does not reenable preemption */
preempt_enable();
#endif
if (current->set_child_tid)
put_user(current->pid, current->set_child_tid);
}
/*
* context_switch - switch to the new MM and the new
* thread's register state.
*/
static inline struct task_struct *
context_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
if (unlikely(!mm)) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
if (unlikely(!prev->mm)) {
prev->active_mm = NULL;
WARN_ON(rq->prev_mm);
rq->prev_mm = oldmm;
}
/*
* Since the runqueue lock will be released by the next
* task (which is an invalid locking op but in the case
* of the scheduler it's an obvious special-case), so we
* do an early lockdep release here:
*/
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#endif
/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);
return prev;
}
/*
* nr_running, nr_uninterruptible and nr_context_switches:
*
* externally visible scheduler statistics: current number of runnable
* threads, current number of uninterruptible-sleeping threads, total
* number of context switches performed since bootup.
*/
unsigned long nr_running(void)
{
unsigned long i, sum = 0;
for_each_online_cpu(i)
sum += cpu_rq(i)->nr_running;
return sum;
}
unsigned long nr_uninterruptible(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_uninterruptible;
/*
* Since we read the counters lockless, it might be slightly
* inaccurate. Do not allow it to go below zero though:
*/
if (unlikely((long)sum < 0))
sum = 0;
return sum;
}
unsigned long long nr_context_switches(void)
{
int i;
unsigned long long sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_switches;
return sum;
}
unsigned long nr_iowait(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += atomic_read(&cpu_rq(i)->nr_iowait);
return sum;
}
unsigned long nr_active(void)
{
unsigned long i, running = 0, uninterruptible = 0;
for_each_online_cpu(i) {
running += cpu_rq(i)->nr_running;
uninterruptible += cpu_rq(i)->nr_uninterruptible;
}
if (unlikely((long)uninterruptible < 0))
uninterruptible = 0;
return running + uninterruptible;
}
#ifdef CONFIG_SMP
/*
* Is this task likely cache-hot:
*/
static inline int
task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd)
{
return (long long)(now - p->last_ran) < (long long)sd->cache_hot_time;
}
/*
* double_rq_lock - safely lock two runqueues
*
* Note this does not disable interrupts like task_rq_lock,
* you need to do so manually before calling.
*/
static void double_rq_lock(struct rq *rq1, struct rq *rq2)
__acquires(rq1->lock)
__acquires(rq2->lock)
{
if (rq1 == rq2) {
spin_lock(&rq1->lock);
__acquire(rq2->lock); /* Fake it out ;) */
} else {
if (rq1 < rq2) {
spin_lock(&rq1->lock);
spin_lock(&rq2->lock);
} else {
spin_lock(&rq2->lock);
spin_lock(&rq1->lock);
}
}
}
/*
* double_rq_unlock - safely unlock two runqueues
*
* Note this does not restore interrupts like task_rq_unlock,
* you need to do so manually after calling.
*/
static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
__releases(rq1->lock)
__releases(rq2->lock)
{
spin_unlock(&rq1->lock);
if (rq1 != rq2)
spin_unlock(&rq2->lock);
else
__release(rq2->lock);
}
/*
* double_lock_balance - lock the busiest runqueue, this_rq is locked already.
*/
static void double_lock_balance(struct rq *this_rq, struct rq *busiest)
__releases(this_rq->lock)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest < this_rq) {
spin_unlock(&this_rq->lock);
spin_lock(&busiest->lock);
spin_lock(&this_rq->lock);
} else
spin_lock(&busiest->lock);
}
}
/*
* If dest_cpu is allowed for this process, migrate the task to it.
* This is accomplished by forcing the cpu_allowed mask to only
* allow dest_cpu, which will force the cpu onto dest_cpu. Then
* the cpu_allowed mask is restored.
*/
static void sched_migrate_task(struct task_struct *p, int dest_cpu)
{
struct migration_req req;
unsigned long flags;
struct rq *rq;
rq = task_rq_lock(p, &flags);
if (!cpu_isset(dest_cpu, p->cpus_allowed)
|| unlikely(cpu_is_offline(dest_cpu)))
goto out;
/* force the process onto the specified CPU */
if (migrate_task(p, dest_cpu, &req)) {
/* Need to wait for migration thread (might exit: take ref). */
struct task_struct *mt = rq->migration_thread;
get_task_struct(mt);
task_rq_unlock(rq, &flags);
wake_up_process(mt);
put_task_struct(mt);
wait_for_completion(&req.done);
return;
}
out:
task_rq_unlock(rq, &flags);
}
/*
* sched_exec - execve() is a valuable balancing opportunity, because at
* this point the task has the smallest effective memory and cache footprint.
*/
void sched_exec(void)
{
int new_cpu, this_cpu = get_cpu();
new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
put_cpu();
if (new_cpu != this_cpu)
sched_migrate_task(current, new_cpu);
}
/*
* pull_task - move a task from a remote runqueue to the local runqueue.
* Both runqueues must be locked.
*/
static void pull_task(struct rq *src_rq, struct prio_array *src_array,
struct task_struct *p, struct rq *this_rq,
struct prio_array *this_array, int this_cpu)
{
dequeue_task(p, src_array);
dec_nr_running(p, src_rq);
set_task_cpu(p, this_cpu);
inc_nr_running(p, this_rq);
enqueue_task(p, this_array);
p->timestamp = (p->timestamp - src_rq->timestamp_last_tick)
+ this_rq->timestamp_last_tick;
/*
* Note that idle threads have a prio of MAX_PRIO, for this test
* to be always true for them.
*/
if (TASK_PREEMPTS_CURR(p, this_rq))
resched_task(this_rq->curr);
}
/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
struct sched_domain *sd, enum idle_type idle,
int *all_pinned)
{
/*
* We do not migrate tasks that are:
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
*all_pinned = 0;
if (task_running(rq, p))
return 0;
/*
* Aggressive migration if:
* 1) task is cache cold, or
* 2) too many balance attempts have failed.
*/
if (sd->nr_balance_failed > sd->cache_nice_tries)
return 1;
if (task_hot(p, rq->timestamp_last_tick, sd))
return 0;
return 1;
}
#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
/*
* move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
* load from busiest to this_rq, as part of a balancing operation within
* "domain". Returns the number of tasks moved.
*
* Called with both runqueues locked.
*/
static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
unsigned long max_nr_move, unsigned long max_load_move,
struct sched_domain *sd, enum idle_type idle,
int *all_pinned)
{
int idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
best_prio_seen, skip_for_load;
struct prio_array *array, *dst_array;
struct list_head *head, *curr;
struct task_struct *tmp;
long rem_load_move;
if (max_nr_move == 0 || max_load_move == 0)
goto out;
rem_load_move = max_load_move;
pinned = 1;
this_best_prio = rq_best_prio(this_rq);
best_prio = rq_best_prio(busiest);
/*
* Enable handling of the case where there is more than one task
* with the best priority. If the current running task is one
* of those with prio==best_prio we know it won't be moved
* and therefore it's safe to override the skip (based on load) of
* any task we find with that prio.
*/
best_prio_seen = best_prio == busiest->curr->prio;
/*
* We first consider expired tasks. Those will likely not be
* executed in the near future, and they are most likely to
* be cache-cold, thus switching CPUs has the least effect
* on them.
*/
if (busiest->expired->nr_active) {
array = busiest->expired;
dst_array = this_rq->expired;
} else {
array = busiest->active;
dst_array = this_rq->active;
}
new_array:
/* Start searching at priority 0: */
idx = 0;
skip_bitmap:
if (!idx)
idx = sched_find_first_bit(array->bitmap);
else
idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
if (idx >= MAX_PRIO) {
if (array == busiest->expired && busiest->active->nr_active) {
array = busiest->active;
dst_array = this_rq->active;
goto new_array;
}
goto out;
}
head = array->queue + idx;
curr = head->prev;
skip_queue:
tmp = list_entry(curr, struct task_struct, run_list);
curr = curr->prev;
/*
* To help distribute high priority tasks accross CPUs we don't
* skip a task if it will be the highest priority task (i.e. smallest
* prio value) on its new queue regardless of its load weight
*/
skip_for_load = tmp->load_weight > rem_load_move;
if (skip_for_load && idx < this_best_prio)
skip_for_load = !best_prio_seen && idx == best_prio;
if (skip_for_load ||
!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
best_prio_seen |= idx == best_prio;
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
#ifdef CONFIG_SCHEDSTATS
if (task_hot(tmp, busiest->timestamp_last_tick, sd))
schedstat_inc(sd, lb_hot_gained[idle]);
#endif
pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
pulled++;
rem_load_move -= tmp->load_weight;
/*
* We only want to steal up to the prescribed number of tasks
* and the prescribed amount of weighted load.
*/
if (pulled < max_nr_move && rem_load_move > 0) {
if (idx < this_best_prio)
this_best_prio = idx;
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
out:
/*
* Right now, this is the only place pull_task() is called,
* so we can safely collect pull_task() stats here rather than
* inside pull_task().
*/
schedstat_add(sd, lb_gained[idle], pulled);
if (all_pinned)
*all_pinned = pinned;
return pulled;
}
/*
* find_busiest_group finds and returns the busiest CPU group within the
* domain. It calculates and returns the amount of weighted load which
* should be moved to restore balance via the imbalance parameter.
*/
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
unsigned long *imbalance, enum idle_type idle, int *sd_idle,
cpumask_t *cpus)
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
unsigned long max_pull;
unsigned long busiest_load_per_task, busiest_nr_running;
unsigned long this_load_per_task, this_nr_running;
int load_idx;
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
int power_savings_balance = 1;
unsigned long leader_nr_running = 0, min_load_per_task = 0;
unsigned long min_nr_running = ULONG_MAX;
struct sched_group *group_min = NULL, *group_leader = NULL;
#endif
max_load = this_load = total_load = total_pwr = 0;
busiest_load_per_task = busiest_nr_running = 0;
this_load_per_task = this_nr_running = 0;
if (idle == NOT_IDLE)
load_idx = sd->busy_idx;
else if (idle == NEWLY_IDLE)
load_idx = sd->newidle_idx;
else
load_idx = sd->idle_idx;
do {
unsigned long load, group_capacity;
int local_group;
int i;
unsigned long sum_nr_running, sum_weighted_load;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
sum_weighted_load = sum_nr_running = avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
struct rq *rq;
if (!cpu_isset(i, *cpus))
continue;
rq = cpu_rq(i);
if (*sd_idle && !idle_cpu(i))
*sd_idle = 0;
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i, load_idx);
else
load = source_load(i, load_idx);
avg_load += load;
sum_nr_running += rq->nr_running;
sum_weighted_load += rq->raw_weighted_load;
}
total_load += avg_load;
total_pwr += group->cpu_power;
/* Adjust by relative CPU power of the group */
avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
group_capacity = group->cpu_power / SCHED_LOAD_SCALE;
if (local_group) {
this_load = avg_load;
this = group;
this_nr_running = sum_nr_running;
this_load_per_task = sum_weighted_load;
} else if (avg_load > max_load &&
sum_nr_running > group_capacity) {
max_load = avg_load;
busiest = group;
busiest_nr_running = sum_nr_running;
busiest_load_per_task = sum_weighted_load;
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/*
* Busy processors will not participate in power savings
* balance.
*/
if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
goto group_next;
/*
* If the local group is idle or completely loaded
* no need to do power savings balance at this domain
*/
if (local_group && (this_nr_running >= group_capacity ||
!this_nr_running))
power_savings_balance = 0;
/*
* If a group is already running at full capacity or idle,
* don't include that group in power savings calculations
*/
if (!power_savings_balance || sum_nr_running >= group_capacity
|| !sum_nr_running)
goto group_next;
/*
* Calculate the group which has the least non-idle load.
* This is the group from where we need to pick up the load
* for saving power
*/
if ((sum_nr_running < min_nr_running) ||
(sum_nr_running == min_nr_running &&
first_cpu(group->cpumask) <
first_cpu(group_min->cpumask))) {
group_min = group;
min_nr_running = sum_nr_running;
min_load_per_task = sum_weighted_load /
sum_nr_running;
}
/*
* Calculate the group which is almost near its
* capacity but still has some space to pick up some load
* from other group and save more power
*/
if (sum_nr_running <= group_capacity - 1) {
if (sum_nr_running > leader_nr_running ||
(sum_nr_running == leader_nr_running &&
first_cpu(group->cpumask) >
first_cpu(group_leader->cpumask))) {
group_leader = group;
leader_nr_running = sum_nr_running;
}
}
group_next:
#endif
group = group->next;
} while (group != sd->groups);
if (!busiest || this_load >= max_load || busiest_nr_running == 0)
goto out_balanced;
avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
if (this_load >= avg_load ||
100*max_load <= sd->imbalance_pct*this_load)
goto out_balanced;
busiest_load_per_task /= busiest_nr_running;
/*
* We're trying to get all the cpus to the average_load, so we don't
* want to push ourselves above the average load, nor do we wish to
* reduce the max loaded cpu below the average load, as either of these
* actions would just result in more rebalancing later, and ping-pong
* tasks around. Thus we look for the minimum possible imbalance.
* Negative imbalances (*we* are more loaded than anyone else) will
* be counted as no imbalance for these purposes -- we can't fix that
* by pulling tasks to us. Be careful of negative numbers as they'll
* appear as very large values with unsigned longs.
*/
if (max_load <= busiest_load_per_task)
goto out_balanced;
/*
* In the presence of smp nice balancing, certain scenarios can have
* max load less than avg load(as we skip the groups at or below
* its cpu_power, while calculating max_load..)
*/
if (max_load < avg_load) {
*imbalance = 0;
goto small_imbalance;
}
/* Don't want to pull so many tasks that a group would go idle */
max_pull = min(max_load - avg_load, max_load - busiest_load_per_task);
/* How much load to actually move to equalise the imbalance */
*imbalance = min(max_pull * busiest->cpu_power,
(avg_load - this_load) * this->cpu_power)
/ SCHED_LOAD_SCALE;
/*
* if *imbalance is less than the average load per runnable task
* there is no gaurantee that any tasks will be moved so we'll have
* a think about bumping its value to force at least one task to be
* moved
*/
if (*imbalance < busiest_load_per_task) {
unsigned long tmp, pwr_now, pwr_move;
unsigned int imbn;
small_imbalance:
pwr_move = pwr_now = 0;
imbn = 2;
if (this_nr_running) {
this_load_per_task /= this_nr_running;
if (busiest_load_per_task > this_load_per_task)
imbn = 1;
} else
this_load_per_task = SCHED_LOAD_SCALE;
if (max_load - this_load >= busiest_load_per_task * imbn) {
*imbalance = busiest_load_per_task;
return busiest;
}
/*
* OK, we don't have enough imbalance to justify moving tasks,
* however we may be able to increase total CPU power used by
* moving them.
*/
pwr_now += busiest->cpu_power *
min(busiest_load_per_task, max_load);
pwr_now += this->cpu_power *
min(this_load_per_task, this_load);
pwr_now /= SCHED_LOAD_SCALE;
/* Amount of load we'd subtract */
tmp = busiest_load_per_task*SCHED_LOAD_SCALE/busiest->cpu_power;
if (max_load > tmp)
pwr_move += busiest->cpu_power *
min(busiest_load_per_task, max_load - tmp);
/* Amount of load we'd add */
if (max_load*busiest->cpu_power <
busiest_load_per_task*SCHED_LOAD_SCALE)
tmp = max_load*busiest->cpu_power/this->cpu_power;
else
tmp = busiest_load_per_task*SCHED_LOAD_SCALE/this->cpu_power;
pwr_move += this->cpu_power*min(this_load_per_task, this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain throughput */
if (pwr_move <= pwr_now)
goto out_balanced;
*imbalance = busiest_load_per_task;
}
return busiest;
out_balanced:
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
goto ret;
if (this == group_leader && group_leader != group_min) {
*imbalance = min_load_per_task;
return group_min;
}
ret:
#endif
*imbalance = 0;
return NULL;
}
/*
* find_busiest_queue - find the busiest runqueue among the cpus in group.
*/
static struct rq *
find_busiest_queue(struct sched_group *group, enum idle_type idle,
unsigned long imbalance, cpumask_t *cpus)
{
struct rq *busiest = NULL, *rq;
unsigned long max_load = 0;
int i;
for_each_cpu_mask(i, group->cpumask) {
if (!cpu_isset(i, *cpus))
continue;
rq = cpu_rq(i);
if (rq->nr_running == 1 && rq->raw_weighted_load > imbalance)
continue;
if (rq->raw_weighted_load > max_load) {
max_load = rq->raw_weighted_load;
busiest = rq;
}
}
return busiest;
}
/*
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
* so long as it is large enough.
*/
#define MAX_PINNED_INTERVAL 512
static inline unsigned long minus_1_or_zero(unsigned long n)
{
return n > 0 ? n - 1 : 0;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
* Called with this_rq unlocked.
*/
static int load_balance(int this_cpu, struct rq *this_rq,
struct sched_domain *sd, enum idle_type idle)
{
int nr_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
struct sched_group *group;
unsigned long imbalance;
struct rq *busiest;
cpumask_t cpus = CPU_MASK_ALL;
if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
!sched_smt_power_savings)
sd_idle = 1;
schedstat_inc(sd, lb_cnt[idle]);
redo:
group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
&cpus);
if (!group) {
schedstat_inc(sd, lb_nobusyg[idle]);
goto out_balanced;
}
busiest = find_busiest_queue(group, idle, imbalance, &cpus);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[idle]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[idle], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
* an imbalance but busiest->nr_running <= 1, the group is
* still unbalanced. nr_moved simply stays zero, so it is
* correctly treated as an imbalance.
*/
double_rq_lock(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
minus_1_or_zero(busiest->nr_running),
imbalance, sd, idle, &all_pinned);
double_rq_unlock(this_rq, busiest);
/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(all_pinned)) {
cpu_clear(cpu_of(busiest), cpus);
if (!cpus_empty(cpus))
goto redo;
goto out_balanced;
}
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[idle]);
sd->nr_balance_failed++;
if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
spin_lock(&busiest->lock);
/* don't kick the migration_thread, if the curr
* task on busiest cpu can't be moved to this_cpu
*/
if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
spin_unlock(&busiest->lock);
all_pinned = 1;
goto out_one_pinned;
}
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
active_balance = 1;
}
spin_unlock(&busiest->lock);
if (active_balance)
wake_up_process(busiest->migration_thread);
/*
* We've kicked active balancing, reset the failure
* counter.
*/
sd->nr_balance_failed = sd->cache_nice_tries+1;
}
} else
sd->nr_balance_failed = 0;
if (likely(!active_balance)) {
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
} else {
/*
* If we've begun active balancing, start to back off. This
* case may not be covered by the all_pinned logic if there
* is only 1 task on the busy runqueue (because we don't call
* move_tasks).
*/
if (sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
}
if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!sched_smt_power_savings)
return -1;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[idle]);
sd->nr_balance_failed = 0;
out_one_pinned:
/* tune up the balancing interval */
if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
(sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!sched_smt_power_savings)
return -1;
return 0;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
* Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
* this_rq is locked.
*/
static int
load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
{
struct sched_group *group;
struct rq *busiest = NULL;
unsigned long imbalance;
int nr_moved = 0;
int sd_idle = 0;
cpumask_t cpus = CPU_MASK_ALL;
if (sd->flags & SD_SHARE_CPUPOWER && !sched_smt_power_savings)
sd_idle = 1;
schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
redo:
group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE,
&sd_idle, &cpus);
if (!group) {
schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
goto out_balanced;
}
busiest = find_busiest_queue(group, NEWLY_IDLE, imbalance,
&cpus);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
minus_1_or_zero(busiest->nr_running),
imbalance, sd, NEWLY_IDLE, NULL);
spin_unlock(&busiest->lock);
if (!nr_moved) {
cpu_clear(cpu_of(busiest), cpus);
if (!cpus_empty(cpus))
goto redo;
}
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER)
return -1;
} else
sd->nr_balance_failed = 0;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!sched_smt_power_savings)
return -1;
sd->nr_balance_failed = 0;
return 0;
}
/*
* idle_balance is called by schedule() if this_cpu is about to become
* idle. Attempts to pull tasks from other CPUs.
*/
static void idle_balance(int this_cpu, struct rq *this_rq)
{
struct sched_domain *sd;
for_each_domain(this_cpu, sd) {
if (sd->flags & SD_BALANCE_NEWIDLE) {
/* If we've pulled tasks over stop searching: */
if (load_balance_newidle(this_cpu, this_rq, sd))
break;
}
}
}
/*
* active_load_balance is run by migration threads. It pushes running tasks
* off the busiest CPU onto idle CPUs. It requires at least 1 task to be
* running on each physical CPU where possible, and avoids physical /
* logical imbalances.
*
* Called with busiest_rq locked.
*/
static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
{
int target_cpu = busiest_rq->push_cpu;
struct sched_domain *sd;
struct rq *target_rq;
/* Is there any task to move? */
if (busiest_rq->nr_running <= 1)
return;
target_rq = cpu_rq(target_cpu);
/*
* This condition is "impossible", if it occurs
* we need to fix it. Originally reported by
* Bjorn Helgaas on a 128-cpu setup.
*/
BUG_ON(busiest_rq == target_rq);
/* move a task from busiest_rq to target_rq */
double_lock_balance(busiest_rq, target_rq);
/* Search for an sd spanning us and the target CPU. */
for_each_domain(target_cpu, sd) {
if ((sd->flags & SD_LOAD_BALANCE) &&
cpu_isset(busiest_cpu, sd->span))
break;
}
if (likely(sd)) {
schedstat_inc(sd, alb_cnt);
if (move_tasks(target_rq, target_cpu, busiest_rq, 1,
RTPRIO_TO_LOAD_WEIGHT(100), sd, SCHED_IDLE,
NULL))
schedstat_inc(sd, alb_pushed);
else
schedstat_inc(sd, alb_failed);
}
spin_unlock(&target_rq->lock);
}
/*
* rebalance_tick will get called every timer tick, on every CPU.
*
* It checks each scheduling domain to see if it is due to be balanced,
* and initiates a balancing operation if so.
*
* Balancing parameters are set up in arch_init_sched_domains.
*/
/* Don't have all balancing operations going off at once: */
static inline unsigned long cpu_offset(int cpu)
{
return jiffies + cpu * HZ / NR_CPUS;
}
static void
rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
{
unsigned long this_load, interval, j = cpu_offset(this_cpu);
struct sched_domain *sd;
int i, scale;
this_load = this_rq->raw_weighted_load;
/* Update our load: */
for (i = 0, scale = 1; i < 3; i++, scale <<= 1) {
unsigned long old_load, new_load;
old_load = this_rq->cpu_load[i];
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
if (new_load > old_load)
new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
}
for_each_domain(this_cpu, sd) {
if (!(sd->flags & SD_LOAD_BALANCE))
continue;
interval = sd->balance_interval;
if (idle != SCHED_IDLE)
interval *= sd->busy_factor;
/* scale ms to jiffies */
interval = msecs_to_jiffies(interval);
if (unlikely(!interval))
interval = 1;
if (j - sd->last_balance >= interval) {
if (load_balance(this_cpu, this_rq, sd, idle)) {
/*
* We've pulled tasks over so either we're no
* longer idle, or one of our SMT siblings is
* not idle.
*/
idle = NOT_IDLE;
}
sd->last_balance += interval;
}
}
}
#else
/*
* on UP we do not need to balance between CPUs:
*/
static inline void rebalance_tick(int cpu, struct rq *rq, enum idle_type idle)
{
}
static inline void idle_balance(int cpu, struct rq *rq)
{
}
#endif
static inline int wake_priority_sleeper(struct rq *rq)
{
int ret = 0;
#ifdef CONFIG_SCHED_SMT
spin_lock(&rq->lock);
/*
* If an SMT sibling task has been put to sleep for priority
* reasons reschedule the idle task to see if it can now run.
*/
if (rq->nr_running) {
resched_task(rq->idle);
ret = 1;
}
spin_unlock(&rq->lock);
#endif
return ret;
}
DEFINE_PER_CPU(struct kernel_stat, kstat);
EXPORT_PER_CPU_SYMBOL(kstat);
/*
* This is called on clock ticks and on context switches.
* Bank in p->sched_time the ns elapsed since the last tick or switch.
*/
static inline void
update_cpu_clock(struct task_struct *p, struct rq *rq, unsigned long long now)
{
p->sched_time += now - max(p->timestamp, rq->timestamp_last_tick);
}
/*
* Return current->sched_time plus any more ns on the sched_clock
* that have not yet been banked.
*/
unsigned long long current_sched_time(const struct task_struct *p)
{
unsigned long long ns;
unsigned long flags;
local_irq_save(flags);
ns = max(p->timestamp, task_rq(p)->timestamp_last_tick);
ns = p->sched_time + sched_clock() - ns;
local_irq_restore(flags);
return ns;
}
/*
* We place interactive tasks back into the active array, if possible.
*
* To guarantee that this does not starve expired tasks we ignore the
* interactivity of a task if the first expired task had to wait more
* than a 'reasonable' amount of time. This deadline timeout is
* load-dependent, as the frequency of array switched decreases with
* increasing number of running tasks. We also ignore the interactivity
* if a better static_prio task has expired:
*/
static inline int expired_starving(struct rq *rq)
{
if (rq->curr->static_prio > rq->best_expired_prio)
return 1;
if (!STARVATION_LIMIT || !rq->expired_timestamp)
return 0;
if (jiffies - rq->expired_timestamp > STARVATION_LIMIT * rq->nr_running)
return 1;
return 0;
}
/*
* Account user cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in user space since the last update
*/
void account_user_time(struct task_struct *p, cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp;
p->utime = cputime_add(p->utime, cputime);
/* Add user time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (TASK_NICE(p) > 0)
cpustat->nice = cputime64_add(cpustat->nice, tmp);
else
cpustat->user = cputime64_add(cpustat->user, tmp);
}
/*
* Account system cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in kernel space since the last update
*/
void account_system_time(struct task_struct *p, int hardirq_offset,
cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
struct rq *rq = this_rq();
cputime64_t tmp;
p->stime = cputime_add(p->stime, cputime);
/* Add system time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (hardirq_count() - hardirq_offset)
cpustat->irq = cputime64_add(cpustat->irq, tmp);
else if (softirq_count())
cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
else if (p != rq->idle)
cpustat->system = cputime64_add(cpustat->system, tmp);
else if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
/* Account for system time used */
acct_update_integrals(p);
}
/*
* Account for involuntary wait time.
* @p: the process from which the cpu time has been stolen
* @steal: the cpu time spent in involuntary wait
*/
void account_steal_time(struct task_struct *p, cputime_t steal)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp = cputime_to_cputime64(steal);
struct rq *rq = this_rq();
if (p == rq->idle) {
p->stime = cputime_add(p->stime, steal);
if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
} else
cpustat->steal = cputime64_add(cpustat->steal, tmp);
}
/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
*
* It also gets called by the fork code, when changing the parent's
* timeslices.
*/
void scheduler_tick(void)
{
unsigned long long now = sched_clock();
struct task_struct *p = current;
int cpu = smp_processor_id();
struct rq *rq = cpu_rq(cpu);
update_cpu_clock(p, rq, now);
rq->timestamp_last_tick = now;
if (p == rq->idle) {
if (wake_priority_sleeper(rq))
goto out;
rebalance_tick(cpu, rq, SCHED_IDLE);
return;
}
/* Task might have expired already, but not scheduled off yet */
if (p->array != rq->active) {
set_tsk_need_resched(p);
goto out;
}
spin_lock(&rq->lock);
/*
* The task was running during this tick - update the
* time slice counter. Note: we do not update a thread's
* priority until it either goes to sleep or uses up its
* timeslice. This makes it possible for interactive tasks
* to use up their timeslices at their highest priority levels.
*/
if (rt_task(p)) {
/*
* RR tasks need a special form of timeslice management.
* FIFO tasks have no timeslices.
*/
if ((p->policy == SCHED_RR) && !--p->time_slice) {
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
set_tsk_need_resched(p);
/* put it at the end of the queue: */
requeue_task(p, rq->active);
}
goto out_unlock;
}
if (!--p->time_slice) {
dequeue_task(p, rq->active);
set_tsk_need_resched(p);
p->prio = effective_prio(p);
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
enqueue_task(p, rq->expired);
if (p->static_prio < rq->best_expired_prio)
rq->best_expired_prio = p->static_prio;
} else
enqueue_task(p, rq->active);
} else {
/*
* Prevent a too long timeslice allowing a task to monopolize
* the CPU. We do this by splitting up the timeslice into
* smaller pieces.
*
* Note: this does not mean the task's timeslices expire or
* get lost in any way, they just might be preempted by
* another task of equal priority. (one with higher
* priority would have preempted this task already.) We
* requeue this task to the end of the list on this priority
* level, which is in essence a round-robin of tasks with
* equal priority.
*
* This only applies to tasks in the interactive
* delta range with at least TIMESLICE_GRANULARITY to requeue.
*/
if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
(p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
(p->array == rq->active)) {
requeue_task(p, rq->active);
set_tsk_need_resched(p);
}
}
out_unlock:
spin_unlock(&rq->lock);
out:
rebalance_tick(cpu, rq, NOT_IDLE);
}
#ifdef CONFIG_SCHED_SMT
static inline void wakeup_busy_runqueue(struct rq *rq)
{
/* If an SMT runqueue is sleeping due to priority reasons wake it up */
if (rq->curr == rq->idle && rq->nr_running)
resched_task(rq->idle);
}
/*
* Called with interrupt disabled and this_rq's runqueue locked.
*/
static void wake_sleeping_dependent(int this_cpu)
{
struct sched_domain *tmp, *sd = NULL;
int i;
for_each_domain(this_cpu, tmp) {
if (tmp->flags & SD_SHARE_CPUPOWER) {
sd = tmp;
break;
}
}
if (!sd)
return;
for_each_cpu_mask(i, sd->span) {
struct rq *smt_rq = cpu_rq(i);
if (i == this_cpu)
continue;
if (unlikely(!spin_trylock(&smt_rq->lock)))
continue;
wakeup_busy_runqueue(smt_rq);
spin_unlock(&smt_rq->lock);
}
}
/*
* number of 'lost' timeslices this task wont be able to fully
* utilize, if another task runs on a sibling. This models the
* slowdown effect of other tasks running on siblings:
*/
static inline unsigned long
smt_slice(struct task_struct *p, struct sched_domain *sd)
{
return p->time_slice * (100 - sd->per_cpu_gain) / 100;
}
/*
* To minimise lock contention and not have to drop this_rq's runlock we only
* trylock the sibling runqueues and bypass those runqueues if we fail to
* acquire their lock. As we only trylock the normal locking order does not
* need to be obeyed.
*/
static int
dependent_sleeper(int this_cpu, struct rq *this_rq, struct task_struct *p)
{
struct sched_domain *tmp, *sd = NULL;
int ret = 0, i;
/* kernel/rt threads do not participate in dependent sleeping */
if (!p->mm || rt_task(p))
return 0;
for_each_domain(this_cpu, tmp) {
if (tmp->flags & SD_SHARE_CPUPOWER) {
sd = tmp;
break;
}
}
if (!sd)
return 0;
for_each_cpu_mask(i, sd->span) {
struct task_struct *smt_curr;
struct rq *smt_rq;
if (i == this_cpu)
continue;
smt_rq = cpu_rq(i);
if (unlikely(!spin_trylock(&smt_rq->lock)))
continue;
smt_curr = smt_rq->curr;
if (!smt_curr->mm)
goto unlock;
/*
* If a user task with lower static priority than the
* running task on the SMT sibling is trying to schedule,
* delay it till there is proportionately less timeslice
* left of the sibling task to prevent a lower priority
* task from using an unfair proportion of the
* physical cpu's resources. -ck
*/
if (rt_task(smt_curr)) {
/*
* With real time tasks we run non-rt tasks only
* per_cpu_gain% of the time.
*/
if ((jiffies % DEF_TIMESLICE) >
(sd->per_cpu_gain * DEF_TIMESLICE / 100))
ret = 1;
} else {
if (smt_curr->static_prio < p->static_prio &&
!TASK_PREEMPTS_CURR(p, smt_rq) &&
smt_slice(smt_curr, sd) > task_timeslice(p))
ret = 1;
}
unlock:
spin_unlock(&smt_rq->lock);
}
return ret;
}
#else
static inline void wake_sleeping_dependent(int this_cpu)
{
}
static inline int
dependent_sleeper(int this_cpu, struct rq *this_rq, struct task_struct *p)
{
return 0;
}
#endif
#if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
void fastcall add_preempt_count(int val)
{
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
return;
preempt_count() += val;
/*
* Spinlock count overflowing soon?
*/
DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK-10);
}
EXPORT_SYMBOL(add_preempt_count);
void fastcall sub_preempt_count(int val)
{
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
return;
/*
* Is the spinlock portion underflowing?
*/
if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
!(preempt_count() & PREEMPT_MASK)))
return;
preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);
#endif
static inline int interactive_sleep(enum sleep_type sleep_type)
{
return (sleep_type == SLEEP_INTERACTIVE ||
sleep_type == SLEEP_INTERRUPTED);
}
/*
* schedule() is the main scheduler function.
*/
asmlinkage void __sched schedule(void)
{
struct task_struct *prev, *next;
struct prio_array *array;
struct list_head *queue;
unsigned long long now;
unsigned long run_time;
int cpu, idx, new_prio;
long *switch_count;
struct rq *rq;
/*
* Test if we are atomic. Since do_exit() needs to call into
* schedule() atomically, we ignore that path for now.
* Otherwise, whine if we are scheduling when we should not be.
*/
if (unlikely(in_atomic() && !current->exit_state)) {
printk(KERN_ERR "BUG: scheduling while atomic: "
"%s/0x%08x/%d\n",
current->comm, preempt_count(), current->pid);
dump_stack();
}
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
need_resched:
preempt_disable();
prev = current;
release_kernel_lock(prev);
need_resched_nonpreemptible:
rq = this_rq();
/*
* The idle thread is not allowed to schedule!
* Remove this check after it has been exercised a bit.
*/
if (unlikely(prev == rq->idle) && prev->state != TASK_RUNNING) {
printk(KERN_ERR "bad: scheduling from the idle thread!\n");
dump_stack();
}
schedstat_inc(rq, sched_cnt);
now = sched_clock();
if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
run_time = now - prev->timestamp;
if (unlikely((long long)(now - prev->timestamp) < 0))
run_time = 0;
} else
run_time = NS_MAX_SLEEP_AVG;
/*
* Tasks charged proportionately less run_time at high sleep_avg to
* delay them losing their interactive status
*/
run_time /= (CURRENT_BONUS(prev) ? : 1);
spin_lock_irq(&rq->lock);
switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
switch_count = &prev->nvcsw;
if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
unlikely(signal_pending(prev))))
prev->state = TASK_RUNNING;
else {
if (prev->state == TASK_UNINTERRUPTIBLE)
rq->nr_uninterruptible++;
deactivate_task(prev, rq);
}
}
cpu = smp_processor_id();
if (unlikely(!rq->nr_running)) {
idle_balance(cpu, rq);
if (!rq->nr_running) {
next = rq->idle;
rq->expired_timestamp = 0;
wake_sleeping_dependent(cpu);
goto switch_tasks;
}
}
array = rq->active;
if (unlikely(!array->nr_active)) {
/*
* Switch the active and expired arrays.
*/
schedstat_inc(rq, sched_switch);
rq->active = rq->expired;
rq->expired = array;
array = rq->active;
rq->expired_timestamp = 0;
rq->best_expired_prio = MAX_PRIO;
}
idx = sched_find_first_bit(array->bitmap);
queue = array->queue + idx;
next = list_entry(queue->next, struct task_struct, run_list);
if (!rt_task(next) && interactive_sleep(next->sleep_type)) {
unsigned long long delta = now - next->timestamp;
if (unlikely((long long)(now - next->timestamp) < 0))
delta = 0;
if (next->sleep_type == SLEEP_INTERACTIVE)
delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
array = next->array;
new_prio = recalc_task_prio(next, next->timestamp + delta);
if (unlikely(next->prio != new_prio)) {
dequeue_task(next, array);
next->prio = new_prio;
enqueue_task(next, array);
}
}
next->sleep_type = SLEEP_NORMAL;
if (dependent_sleeper(cpu, rq, next))
next = rq->idle;
switch_tasks:
if (next == rq->idle)
schedstat_inc(rq, sched_goidle);
prefetch(next);
prefetch_stack(next);
clear_tsk_need_resched(prev);
rcu_qsctr_inc(task_cpu(prev));
update_cpu_clock(prev, rq, now);
prev->sleep_avg -= run_time;
if ((long)prev->sleep_avg <= 0)
prev->sleep_avg = 0;
prev->timestamp = prev->last_ran = now;
sched_info_switch(prev, next);
if (likely(prev != next)) {
next->timestamp = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
prepare_task_switch(rq, next);
prev = context_switch(rq, prev, next);
barrier();
/*
* this_rq must be evaluated again because prev may have moved
* CPUs since it called schedule(), thus the 'rq' on its stack
* frame will be invalid.
*/
finish_task_switch(this_rq(), prev);
} else
spin_unlock_irq(&rq->lock);
prev = current;
if (unlikely(reacquire_kernel_lock(prev) < 0))
goto need_resched_nonpreemptible;
preempt_enable_no_resched();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_PREEMPT
/*
* this is the entry point to schedule() from in-kernel preemption
* off of preempt_enable. Kernel preemptions off return from interrupt
* occur there and call schedule directly.
*/
asmlinkage void __sched preempt_schedule(void)
{
struct thread_info *ti = current_thread_info();
#ifdef CONFIG_PREEMPT_BKL
struct task_struct *task = current;
int saved_lock_depth;
#endif
/*
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
if (unlikely(ti->preempt_count || irqs_disabled()))
return;
need_resched:
add_preempt_count(PREEMPT_ACTIVE);
/*
* We keep the big kernel semaphore locked, but we
* clear ->lock_depth so that schedule() doesnt
* auto-release the semaphore:
*/
#ifdef CONFIG_PREEMPT_BKL
saved_lock_depth = task->lock_depth;
task->lock_depth = -1;
#endif
schedule();
#ifdef CONFIG_PREEMPT_BKL
task->lock_depth = saved_lock_depth;
#endif
sub_preempt_count(PREEMPT_ACTIVE);
/* we could miss a preemption opportunity between schedule and now */
barrier();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(preempt_schedule);
/*
* this is the entry point to schedule() from kernel preemption
* off of irq context.
* Note, that this is called and return with irqs disabled. This will
* protect us against recursive calling from irq.
*/
asmlinkage void __sched preempt_schedule_irq(void)
{
struct thread_info *ti = current_thread_info();
#ifdef CONFIG_PREEMPT_BKL
struct task_struct *task = current;
int saved_lock_depth;
#endif
/* Catch callers which need to be fixed */
BUG_ON(ti->preempt_count || !irqs_disabled());
need_resched:
add_preempt_count(PREEMPT_ACTIVE);
/*
* We keep the big kernel semaphore locked, but we
* clear ->lock_depth so that schedule() doesnt
* auto-release the semaphore:
*/
#ifdef CONFIG_PREEMPT_BKL
saved_lock_depth = task->lock_depth;
task->lock_depth = -1;
#endif
local_irq_enable();
schedule();
local_irq_disable();
#ifdef CONFIG_PREEMPT_BKL
task->lock_depth = saved_lock_depth;
#endif
sub_preempt_count(PREEMPT_ACTIVE);
/* we could miss a preemption opportunity between schedule and now */
barrier();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
#endif /* CONFIG_PREEMPT */
int default_wake_function(wait_queue_t *curr, unsigned mode, int sync,
void *key)
{
return try_to_wake_up(curr->private, mode, sync);
}
EXPORT_SYMBOL(default_wake_function);
/*
* The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
* wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
* number) then we wake all the non-exclusive tasks and one exclusive task.
*
* There are circumstances in which we can try to wake a task which has already
* started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
* zero in this (rare) case, and we handle it by continuing to scan the queue.
*/
static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, int sync, void *key)
{
struct list_head *tmp, *next;
list_for_each_safe(tmp, next, &q->task_list) {
wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
unsigned flags = curr->flags;
if (curr->func(curr, mode, sync, key) &&
(flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
break;
}
}
/**
* __wake_up - wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
* @key: is directly passed to the wakeup function
*/
void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, void *key)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, 0, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(__wake_up);
/*
* Same as __wake_up but called with the spinlock in wait_queue_head_t held.
*/
void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
{
__wake_up_common(q, mode, 1, 0, NULL);
}
/**
* __wake_up_sync - wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
*
* The sync wakeup differs that the waker knows that it will schedule
* away soon, so while the target thread will be woken up, it will not
* be migrated to another CPU - ie. the two threads are 'synchronized'
* with each other. This can prevent needless bouncing between CPUs.
*
* On UP it can prevent extra preemption.
*/
void fastcall
__wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
unsigned long flags;
int sync = 1;
if (unlikely(!q))
return;
if (unlikely(!nr_exclusive))
sync = 0;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, sync, NULL);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
void fastcall complete(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done++;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
1, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete);
void fastcall complete_all(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done += UINT_MAX/2;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
0, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete_all);
void fastcall __sched wait_for_completion(struct completion *x)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
spin_unlock_irq(&x->wait.lock);
}
EXPORT_SYMBOL(wait_for_completion);
unsigned long fastcall __sched
wait_for_completion_timeout(struct completion *x, unsigned long timeout)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
timeout = schedule_timeout(timeout);
spin_lock_irq(&x->wait.lock);
if (!timeout) {
__remove_wait_queue(&x->wait, &wait);
goto out;
}
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return timeout;
}
EXPORT_SYMBOL(wait_for_completion_timeout);
int fastcall __sched wait_for_completion_interruptible(struct completion *x)
{
int ret = 0;
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
if (signal_pending(current)) {
ret = -ERESTARTSYS;
__remove_wait_queue(&x->wait, &wait);
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return ret;
}
EXPORT_SYMBOL(wait_for_completion_interruptible);
unsigned long fastcall __sched
wait_for_completion_interruptible_timeout(struct completion *x,
unsigned long timeout)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
if (signal_pending(current)) {
timeout = -ERESTARTSYS;
__remove_wait_queue(&x->wait, &wait);
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
timeout = schedule_timeout(timeout);
spin_lock_irq(&x->wait.lock);
if (!timeout) {
__remove_wait_queue(&x->wait, &wait);
goto out;
}
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return timeout;
}
EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
#define SLEEP_ON_VAR \
unsigned long flags; \
wait_queue_t wait; \
init_waitqueue_entry(&wait, current);
#define SLEEP_ON_HEAD \
spin_lock_irqsave(&q->lock,flags); \
__add_wait_queue(q, &wait); \
spin_unlock(&q->lock);
#define SLEEP_ON_TAIL \
spin_lock_irq(&q->lock); \
__remove_wait_queue(q, &wait); \
spin_unlock_irqrestore(&q->lock, flags);
void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(interruptible_sleep_on);
long fastcall __sched
interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(interruptible_sleep_on_timeout);
void fastcall __sched sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(sleep_on);
long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(sleep_on_timeout);
#ifdef CONFIG_RT_MUTEXES
/*
* rt_mutex_setprio - set the current priority of a task
* @p: task
* @prio: prio value (kernel-internal form)
*
* This function changes the 'effective' priority of a task. It does
* not touch ->normal_prio like __setscheduler().
*
* Used by the rt_mutex code to implement priority inheritance logic.
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
struct prio_array *array;
unsigned long flags;
struct rq *rq;
int oldprio;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
oldprio = p->prio;
array = p->array;
if (array)
dequeue_task(p, array);
p->prio = prio;
if (array) {
/*
* If changing to an RT priority then queue it
* in the active array!
*/
if (rt_task(p))
array = rq->active;
enqueue_task(p, array);
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
} else if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
task_rq_unlock(rq, &flags);
}
#endif
void set_user_nice(struct task_struct *p, long nice)
{
struct prio_array *array;
int old_prio, delta;
unsigned long flags;
struct rq *rq;
if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
return;
/*
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
rq = task_rq_lock(p, &flags);
/*
* The RT priorities are set via sched_setscheduler(), but we still
* allow the 'normal' nice value to be set - but as expected
* it wont have any effect on scheduling until the task is
* not SCHED_NORMAL/SCHED_BATCH:
*/
if (has_rt_policy(p)) {
p->static_prio = NICE_TO_PRIO(nice);
goto out_unlock;
}
array = p->array;
if (array) {
dequeue_task(p, array);
dec_raw_weighted_load(rq, p);
}
p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p);
old_prio = p->prio;
p->prio = effective_prio(p);
delta = p->prio - old_prio;
if (array) {
enqueue_task(p, array);
inc_raw_weighted_load(rq, p);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
*/
if (delta < 0 || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
out_unlock:
task_rq_unlock(rq, &flags);
}
EXPORT_SYMBOL(set_user_nice);
/*
* can_nice - check if a task can reduce its nice value
* @p: task
* @nice: nice value
*/
int can_nice(const struct task_struct *p, const int nice)
{
/* convert nice value [19,-20] to rlimit style value [1,40] */
int nice_rlim = 20 - nice;
return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur ||
capable(CAP_SYS_NICE));
}
#ifdef __ARCH_WANT_SYS_NICE
/*
* sys_nice - change the priority of the current process.
* @increment: priority increment
*
* sys_setpriority is a more generic, but much slower function that
* does similar things.
*/
asmlinkage long sys_nice(int increment)
{
long nice, retval;
/*
* Setpriority might change our priority at the same moment.
* We don't have to worry. Conceptually one call occurs first
* and we have a single winner.
*/
if (increment < -40)
increment = -40;
if (increment > 40)
increment = 40;
nice = PRIO_TO_NICE(current->static_prio) + increment;
if (nice < -20)
nice = -20;
if (nice > 19)
nice = 19;
if (increment < 0 && !can_nice(current, nice))
return -EPERM;
retval = security_task_setnice(current, nice);
if (retval)
return retval;
set_user_nice(current, nice);
return 0;
}
#endif
/**
* task_prio - return the priority value of a given task.
* @p: the task in question.
*
* This is the priority value as seen by users in /proc.
* RT tasks are offset by -200. Normal tasks are centered
* around 0, value goes from -16 to +15.
*/
int task_prio(const struct task_struct *p)
{
return p->prio - MAX_RT_PRIO;
}
/**
* task_nice - return the nice value of a given task.
* @p: the task in question.
*/
int task_nice(const struct task_struct *p)
{
return TASK_NICE(p);
}
EXPORT_SYMBOL_GPL(task_nice);
/**
* idle_cpu - is a given cpu idle currently?
* @cpu: the processor in question.
*/
int idle_cpu(int cpu)
{
return cpu_curr(cpu) == cpu_rq(cpu)->idle;
}
/**
* idle_task - return the idle task for a given cpu.
* @cpu: the processor in question.
*/
struct task_struct *idle_task(int cpu)
{
return cpu_rq(cpu)->idle;
}
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
*/
static inline struct task_struct *find_process_by_pid(pid_t pid)
{
return pid ? find_task_by_pid(pid) : current;
}
/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
BUG_ON(p->array);
p->policy = policy;
p->rt_priority = prio;
p->normal_prio = normal_prio(p);
/* we are holding p->pi_lock already */
p->prio = rt_mutex_getprio(p);
/*
* SCHED_BATCH tasks are treated as perpetual CPU hogs:
*/
if (policy == SCHED_BATCH)
p->sleep_avg = 0;
set_load_weight(p);
}
/**
* sched_setscheduler - change the scheduling policy and/or RT priority of
* a thread.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* NOTE: the task may be already dead
*/
int sched_setscheduler(struct task_struct *p, int policy,
struct sched_param *param)
{
int retval, oldprio, oldpolicy = -1;
struct prio_array *array;
unsigned long flags;
struct rq *rq;
/* may grab non-irq protected spin_locks */
BUG_ON(in_interrupt());
recheck:
/* double check policy once rq lock held */
if (policy < 0)
policy = oldpolicy = p->policy;
else if (policy != SCHED_FIFO && policy != SCHED_RR &&
policy != SCHED_NORMAL && policy != SCHED_BATCH)
return -EINVAL;
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL and
* SCHED_BATCH is 0.
*/
if (param->sched_priority < 0 ||
(p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
(!p->mm && param->sched_priority > MAX_RT_PRIO-1))
return -EINVAL;
if (is_rt_policy(policy) != (param->sched_priority != 0))
return -EINVAL;
/*
* Allow unprivileged RT tasks to decrease priority:
*/
if (!capable(CAP_SYS_NICE)) {
if (is_rt_policy(policy)) {
unsigned long rlim_rtprio;
unsigned long flags;
if (!lock_task_sighand(p, &flags))
return -ESRCH;
rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
unlock_task_sighand(p, &flags);
/* can't set/change the rt policy */
if (policy != p->policy && !rlim_rtprio)
return -EPERM;
/* can't increase priority */
if (param->sched_priority > p->rt_priority &&
param->sched_priority > rlim_rtprio)
return -EPERM;
}
/* can't change other user's priorities */
if ((current->euid != p->euid) &&
(current->euid != p->uid))
return -EPERM;
}
retval = security_task_setscheduler(p, policy, param);
if (retval)
return retval;
/*
* make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
*/
spin_lock_irqsave(&p->pi_lock, flags);
/*
* To be able to change p->policy safely, the apropriate
* runqueue lock must be held.
*/
rq = __task_rq_lock(p);
/* recheck policy now with rq lock held */
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
goto recheck;
}
array = p->array;
if (array)
deactivate_task(p, rq);
oldprio = p->prio;
__setscheduler(p, policy, param->sched_priority);
if (array) {
__activate_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
} else if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
rt_mutex_adjust_pi(p);
return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);
static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lparam;
struct task_struct *p;
int retval;
if (!param || pid < 0)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
if (p != NULL)
retval = sched_setscheduler(p, policy, &lparam);
rcu_read_unlock();
return retval;
}
/**
* sys_sched_setscheduler - set/change the scheduler policy and RT priority
* @pid: the pid in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
struct sched_param __user *param)
{
/* negative values for policy are not valid */
if (policy < 0)
return -EINVAL;
return do_sched_setscheduler(pid, policy, param);
}
/**
* sys_sched_setparam - set/change the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
{
return do_sched_setscheduler(pid, -1, param);
}
/**
* sys_sched_getscheduler - get the policy (scheduling class) of a thread
* @pid: the pid in question.
*/
asmlinkage long sys_sched_getscheduler(pid_t pid)
{
struct task_struct *p;
int retval = -EINVAL;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (p) {
retval = security_task_getscheduler(p);
if (!retval)
retval = p->policy;
}
read_unlock(&tasklist_lock);
out_nounlock:
return retval;
}
/**
* sys_sched_getscheduler - get the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the RT priority.
*/
asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
{
struct sched_param lp;
struct task_struct *p;
int retval = -EINVAL;
if (!param || pid < 0)
goto out_nounlock;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
lp.sched_priority = p->rt_priority;
read_unlock(&tasklist_lock);
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
long sched_setaffinity(pid_t pid, cpumask_t new_mask)
{
cpumask_t cpus_allowed;
struct task_struct *p;
int retval;
lock_cpu_hotplug();
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
return -ESRCH;
}
/*
* It is not safe to call set_cpus_allowed with the
* tasklist_lock held. We will bump the task_struct's
* usage count and then drop tasklist_lock.
*/
get_task_struct(p);
read_unlock(&tasklist_lock);
retval = -EPERM;
if ((current->euid != p->euid) && (current->euid != p->uid) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
retval = security_task_setscheduler(p, 0, NULL);
if (retval)
goto out_unlock;
cpus_allowed = cpuset_cpus_allowed(p);
cpus_and(new_mask, new_mask, cpus_allowed);
retval = set_cpus_allowed(p, new_mask);
out_unlock:
put_task_struct(p);
unlock_cpu_hotplug();
return retval;
}
static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
cpumask_t *new_mask)
{
if (len < sizeof(cpumask_t)) {
memset(new_mask, 0, sizeof(cpumask_t));
} else if (len > sizeof(cpumask_t)) {
len = sizeof(cpumask_t);
}
return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}
/**
* sys_sched_setaffinity - set the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to the new cpu mask
*/
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
cpumask_t new_mask;
int retval;
retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
if (retval)
return retval;
return sched_setaffinity(pid, new_mask);
}
/*
* Represents all cpu's present in the system
* In systems capable of hotplug, this map could dynamically grow
* as new cpu's are detected in the system via any platform specific
* method, such as ACPI for e.g.
*/
cpumask_t cpu_present_map __read_mostly;
EXPORT_SYMBOL(cpu_present_map);
#ifndef CONFIG_SMP
cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_online_map);
cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_possible_map);
#endif
long sched_getaffinity(pid_t pid, cpumask_t *mask)
{
struct task_struct *p;
int retval;
lock_cpu_hotplug();
read_lock(&tasklist_lock);
retval = -ESRCH;
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
cpus_and(*mask, p->cpus_allowed, cpu_online_map);
out_unlock:
read_unlock(&tasklist_lock);
unlock_cpu_hotplug();
if (retval)
return retval;
return 0;
}
/**
* sys_sched_getaffinity - get the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to hold the current cpu mask
*/
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
int ret;
cpumask_t mask;
if (len < sizeof(cpumask_t))
return -EINVAL;
ret = sched_getaffinity(pid, &mask);
if (ret < 0)
return ret;
if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
return -EFAULT;
return sizeof(cpumask_t);
}
/**
* sys_sched_yield - yield the current processor to other threads.
*
* this function yields the current CPU by moving the calling thread
* to the expired array. If there are no other threads running on this
* CPU then this function will return.
*/
asmlinkage long sys_sched_yield(void)
{
struct rq *rq = this_rq_lock();
struct prio_array *array = current->array, *target = rq->expired;
schedstat_inc(rq, yld_cnt);
/*
* We implement yielding by moving the task into the expired
* queue.
*
* (special rule: RT tasks will just roundrobin in the active
* array.)
*/
if (rt_task(current))
target = rq->active;
if (array->nr_active == 1) {
schedstat_inc(rq, yld_act_empty);
if (!rq->expired->nr_active)
schedstat_inc(rq, yld_both_empty);
} else if (!rq->expired->nr_active)
schedstat_inc(rq, yld_exp_empty);
if (array != target) {
dequeue_task(current, array);
enqueue_task(current, target);
} else
/*
* requeue_task is cheaper so perform that if possible.
*/
requeue_task(current, array);
/*
* Since we are going to call schedule() anyway, there's
* no need to preempt or enable interrupts:
*/
__release(rq->lock);
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
_raw_spin_unlock(&rq->lock);
preempt_enable_no_resched();
schedule();
return 0;
}
static inline int __resched_legal(int expected_preempt_count)
{
if (unlikely(preempt_count() != expected_preempt_count))
return 0;
if (unlikely(system_state != SYSTEM_RUNNING))
return 0;
return 1;
}
static void __cond_resched(void)
{
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
__might_sleep(__FILE__, __LINE__);
#endif
/*
* The BKS might be reacquired before we have dropped
* PREEMPT_ACTIVE, which could trigger a second
* cond_resched() call.
*/
do {
add_preempt_count(PREEMPT_ACTIVE);
schedule();
sub_preempt_count(PREEMPT_ACTIVE);
} while (need_resched());
}
int __sched cond_resched(void)
{
if (need_resched() && __resched_legal(0)) {
__cond_resched();
return 1;
}
return 0;
}
EXPORT_SYMBOL(cond_resched);
/*
* cond_resched_lock() - if a reschedule is pending, drop the given lock,
* call schedule, and on return reacquire the lock.
*
* This works OK both with and without CONFIG_PREEMPT. We do strange low-level
* operations here to prevent schedule() from being called twice (once via
* spin_unlock(), once by hand).
*/
int cond_resched_lock(spinlock_t *lock)
{
int ret = 0;
if (need_lockbreak(lock)) {
spin_unlock(lock);
cpu_relax();
ret = 1;
spin_lock(lock);
}
if (need_resched() && __resched_legal(1)) {
spin_release(&lock->dep_map, 1, _THIS_IP_);
_raw_spin_unlock(lock);
preempt_enable_no_resched();
__cond_resched();
ret = 1;
spin_lock(lock);
}
return ret;
}
EXPORT_SYMBOL(cond_resched_lock);
int __sched cond_resched_softirq(void)
{
BUG_ON(!in_softirq());
if (need_resched() && __resched_legal(0)) {
raw_local_irq_disable();
_local_bh_enable();
raw_local_irq_enable();
__cond_resched();
local_bh_disable();
return 1;
}
return 0;
}
EXPORT_SYMBOL(cond_resched_softirq);
/**
* yield - yield the current processor to other threads.
*
* this is a shortcut for kernel-space yielding - it marks the
* thread runnable and calls sys_sched_yield().
*/
void __sched yield(void)
{
set_current_state(TASK_RUNNING);
sys_sched_yield();
}
EXPORT_SYMBOL(yield);
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
*
* But don't do that if it is a deliberate, throttling IO wait (this task
* has set its backing_dev_info: the queue against which it should throttle)
*/
void __sched io_schedule(void)
{
struct rq *rq = &__raw_get_cpu_var(runqueues);
delayacct_blkio_start();
atomic_inc(&rq->nr_iowait);
schedule();
atomic_dec(&rq->nr_iowait);
delayacct_blkio_end();
}
EXPORT_SYMBOL(io_schedule);
long __sched io_schedule_timeout(long timeout)
{
struct rq *rq = &__raw_get_cpu_var(runqueues);
long ret;
delayacct_blkio_start();
atomic_inc(&rq->nr_iowait);
ret = schedule_timeout(timeout);
atomic_dec(&rq->nr_iowait);
delayacct_blkio_end();
return ret;
}
/**
* sys_sched_get_priority_max - return maximum RT priority.
* @policy: scheduling class.
*
* this syscall returns the maximum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_max(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = MAX_USER_RT_PRIO-1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
ret = 0;
break;
}
return ret;
}
/**
* sys_sched_get_priority_min - return minimum RT priority.
* @policy: scheduling class.
*
* this syscall returns the minimum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_min(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = 1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
ret = 0;
}
return ret;
}
/**
* sys_sched_rr_get_interval - return the default timeslice of a process.
* @pid: pid of the process.
* @interval: userspace pointer to the timeslice value.
*
* this syscall writes the default timeslice value of a given process
* into the user-space timespec buffer. A value of '0' means infinity.
*/
asmlinkage
long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
{
struct task_struct *p;
int retval = -EINVAL;
struct timespec t;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
jiffies_to_timespec(p->policy == SCHED_FIFO ?
0 : task_timeslice(p), &t);
read_unlock(&tasklist_lock);
retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
static inline struct task_struct *eldest_child(struct task_struct *p)
{
if (list_empty(&p->children))
return NULL;
return list_entry(p->children.next,struct task_struct,sibling);
}
static inline struct task_struct *older_sibling(struct task_struct *p)
{
if (p->sibling.prev==&p->parent->children)
return NULL;
return list_entry(p->sibling.prev,struct task_struct,sibling);
}
static inline struct task_struct *younger_sibling(struct task_struct *p)
{
if (p->sibling.next==&p->parent->children)
return NULL;
return list_entry(p->sibling.next,struct task_struct,sibling);
}
static const char stat_nam[] = "RSDTtZX";
static void show_task(struct task_struct *p)
{
struct task_struct *relative;
unsigned long free = 0;
unsigned state;
state = p->state ? __ffs(p->state) + 1 : 0;
printk("%-13.13s %c", p->comm,
state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if (BITS_PER_LONG == 32)
if (state == TASK_RUNNING)
printk(" running ");
else
printk(" %08lX ", thread_saved_pc(p));
#else
if (state == TASK_RUNNING)
printk(" running task ");
else
printk(" %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
{
unsigned long *n = end_of_stack(p);
while (!*n)
n++;
free = (unsigned long)n - (unsigned long)end_of_stack(p);
}
#endif
printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
if ((relative = eldest_child(p)))
printk("%5d ", relative->pid);
else
printk(" ");
if ((relative = younger_sibling(p)))
printk("%7d", relative->pid);
else
printk(" ");
if ((relative = older_sibling(p)))
printk(" %5d", relative->pid);
else
printk(" ");
if (!p->mm)
printk(" (L-TLB)\n");
else
printk(" (NOTLB)\n");
if (state != TASK_RUNNING)
show_stack(p, NULL);
}
void show_state(void)
{
struct task_struct *g, *p;
#if (BITS_PER_LONG == 32)
printk("\n"
" sibling\n");
printk(" task PC pid father child younger older\n");
#else
printk("\n"
" sibling\n");
printk(" task PC pid father child younger older\n");
#endif
read_lock(&tasklist_lock);
do_each_thread(g, p) {
/*
* reset the NMI-timeout, listing all files on a slow
* console might take alot of time:
*/
touch_nmi_watchdog();
show_task(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
debug_show_all_locks();
}
/**
* init_idle - set up an idle thread for a given CPU
* @idle: task in question
* @cpu: cpu the idle task belongs to
*
* NOTE: this function does not set the idle thread's NEED_RESCHED
* flag, to make booting more robust.
*/
void __devinit init_idle(struct task_struct *idle, int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
idle->timestamp = sched_clock();
idle->sleep_avg = 0;
idle->array = NULL;
idle->prio = idle->normal_prio = MAX_PRIO;
idle->state = TASK_RUNNING;
idle->cpus_allowed = cpumask_of_cpu(cpu);
set_task_cpu(idle, cpu);
spin_lock_irqsave(&rq->lock, flags);
rq->curr = rq->idle = idle;
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
idle->oncpu = 1;
#endif
spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
#if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)
task_thread_info(idle)->preempt_count = (idle->lock_depth >= 0);
#else
task_thread_info(idle)->preempt_count = 0;
#endif
}
/*
* In a system that switches off the HZ timer nohz_cpu_mask
* indicates which cpus entered this state. This is used
* in the rcu update to wait only for active cpus. For system
* which do not switch off the HZ timer nohz_cpu_mask should
* always be CPU_MASK_NONE.
*/
cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
#ifdef CONFIG_SMP
/*
* This is how migration works:
*
* 1) we queue a struct migration_req structure in the source CPU's
* runqueue and wake up that CPU's migration thread.
* 2) we down() the locked semaphore => thread blocks.
* 3) migration thread wakes up (implicitly it forces the migrated
* thread off the CPU)
* 4) it gets the migration request and checks whether the migrated
* task is still in the wrong runqueue.
* 5) if it's in the wrong runqueue then the migration thread removes
* it and puts it into the right queue.
* 6) migration thread up()s the semaphore.
* 7) we wake up and the migration is done.
*/
/*
* Change a given task's CPU affinity. Migrate the thread to a
* proper CPU and schedule it away if the CPU it's executing on
* is removed from the allowed bitmask.
*
* NOTE: the caller must have a valid reference to the task, the
* task must not exit() & deallocate itself prematurely. The
* call is not atomic; no spinlocks may be held.
*/
int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
{
struct migration_req req;
unsigned long flags;
struct rq *rq;
int ret = 0;
rq = task_rq_lock(p, &flags);
if (!cpus_intersects(new_mask, cpu_online_map)) {
ret = -EINVAL;
goto out;
}
p->cpus_allowed = new_mask;
/* Can the task run on the task's current CPU? If so, we're done */
if (cpu_isset(task_cpu(p), new_mask))
goto out;
if (migrate_task(p, any_online_cpu(new_mask), &req)) {
/* Need help from migration thread: drop lock and wait. */
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
wait_for_completion(&req.done);
tlb_migrate_finish(p->mm);
return 0;
}
out:
task_rq_unlock(rq, &flags);
return ret;
}
EXPORT_SYMBOL_GPL(set_cpus_allowed);
/*
* Move (not current) task off this cpu, onto dest cpu. We're doing
* this because either it can't run here any more (set_cpus_allowed()
* away from this CPU, or CPU going down), or because we're
* attempting to rebalance this task on exec (sched_exec).
*
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*
* Returns non-zero if task was successfully migrated.
*/
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
struct rq *rq_dest, *rq_src;
int ret = 0;
if (unlikely(cpu_is_offline(dest_cpu)))
return ret;
rq_src = cpu_rq(src_cpu);
rq_dest = cpu_rq(dest_cpu);
double_rq_lock(rq_src, rq_dest);
/* Already moved. */
if (task_cpu(p) != src_cpu)
goto out;
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
set_task_cpu(p, dest_cpu);
if (p->array) {
/*
* Sync timestamp with rq_dest's before activating.
* The same thing could be achieved by doing this step
* afterwards, and pretending it was a local activate.
* This way is cleaner and logically correct.
*/
p->timestamp = p->timestamp - rq_src->timestamp_last_tick
+ rq_dest->timestamp_last_tick;
deactivate_task(p, rq_src);
__activate_task(p, rq_dest);
if (TASK_PREEMPTS_CURR(p, rq_dest))
resched_task(rq_dest->curr);
}
ret = 1;
out:
double_rq_unlock(rq_src, rq_dest);
return ret;
}
/*
* migration_thread - this is a highprio system thread that performs
* thread migration by bumping thread off CPU then 'pushing' onto
* another runqueue.
*/
static int migration_thread(void *data)
{
int cpu = (long)data;
struct rq *rq;
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
struct migration_req *req;
struct list_head *head;
try_to_freeze();
spin_lock_irq(&rq->lock);
if (cpu_is_offline(cpu)) {
spin_unlock_irq(&rq->lock);
goto wait_to_die;
}
if (rq->active_balance) {
active_load_balance(rq, cpu);
rq->active_balance = 0;
}
head = &rq->migration_queue;
if (list_empty(head)) {
spin_unlock_irq(&rq->lock);
schedule();
set_current_state(TASK_INTERRUPTIBLE);
continue;
}
req = list_entry(head->next, struct migration_req, list);
list_del_init(head->next);
spin_unlock(&rq->lock);
__migrate_task(req->task, cpu, req->dest_cpu);
local_irq_enable();
complete(&req->done);
}
__set_current_state(TASK_RUNNING);
return 0;
wait_to_die:
/* Wait for kthread_stop */
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/* Figure out where task on dead CPU should go, use force if neccessary. */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
{
unsigned long flags;
cpumask_t mask;
struct rq *rq;
int dest_cpu;
restart:
/* On same node? */
mask = node_to_cpumask(cpu_to_node(dead_cpu));
cpus_and(mask, mask, p->cpus_allowed);
dest_cpu = any_online_cpu(mask);
/* On any allowed CPU? */
if (dest_cpu == NR_CPUS)
dest_cpu = any_online_cpu(p->cpus_allowed);
/* No more Mr. Nice Guy. */
if (dest_cpu == NR_CPUS) {
rq = task_rq_lock(p, &flags);
cpus_setall(p->cpus_allowed);
dest_cpu = any_online_cpu(p->cpus_allowed);
task_rq_unlock(rq, &flags);
/*
* Don't tell them about moving exiting tasks or
* kernel threads (both mm NULL), since they never
* leave kernel.
*/
if (p->mm && printk_ratelimit())
printk(KERN_INFO "process %d (%s) no "
"longer affine to cpu%d\n",
p->pid, p->comm, dead_cpu);
}
if (!__migrate_task(p, dead_cpu, dest_cpu))
goto restart;
}
/*
* While a dead CPU has no uninterruptible tasks queued at this point,
* it might still have a nonzero ->nr_uninterruptible counter, because
* for performance reasons the counter is not stricly tracking tasks to
* their home CPUs. So we just add the counter to another CPU's counter,
* to keep the global sum constant after CPU-down:
*/
static void migrate_nr_uninterruptible(struct rq *rq_src)
{
struct rq *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL));
unsigned long flags;
local_irq_save(flags);
double_rq_lock(rq_src, rq_dest);
rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
rq_src->nr_uninterruptible = 0;
double_rq_unlock(rq_src, rq_dest);
local_irq_restore(flags);
}
/* Run through task list and migrate tasks from the dead cpu. */
static void migrate_live_tasks(int src_cpu)
{
struct task_struct *p, *t;
write_lock_irq(&tasklist_lock);
do_each_thread(t, p) {
if (p == current)
continue;
if (task_cpu(p) == src_cpu)
move_task_off_dead_cpu(src_cpu, p);
} while_each_thread(t, p);
write_unlock_irq(&tasklist_lock);
}
/* Schedules idle task to be the next runnable task on current CPU.
* It does so by boosting its priority to highest possible and adding it to
* the _front_ of the runqueue. Used by CPU offline code.
*/
void sched_idle_next(void)
{
int this_cpu = smp_processor_id();
struct rq *rq = cpu_rq(this_cpu);
struct task_struct *p = rq->idle;
unsigned long flags;
/* cpu has to be offline */
BUG_ON(cpu_online(this_cpu));
/*
* Strictly not necessary since rest of the CPUs are stopped by now
* and interrupts disabled on the current cpu.
*/
spin_lock_irqsave(&rq->lock, flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
/* Add idle task to the _front_ of its priority queue: */
__activate_idle_task(p, rq);
spin_unlock_irqrestore(&rq->lock, flags);
}
/*
* Ensures that the idle task is using init_mm right before its cpu goes
* offline.
*/
void idle_task_exit(void)
{
struct mm_struct *mm = current->active_mm;
BUG_ON(cpu_online(smp_processor_id()));
if (mm != &init_mm)
switch_mm(mm, &init_mm, current);
mmdrop(mm);
}
static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(dead_cpu);
/* Must be exiting, otherwise would be on tasklist. */
BUG_ON(p->exit_state != EXIT_ZOMBIE && p->exit_state != EXIT_DEAD);
/* Cannot have done final schedule yet: would have vanished. */
BUG_ON(p->state == TASK_DEAD);
get_task_struct(p);
/*
* Drop lock around migration; if someone else moves it,
* that's OK. No task can be added to this CPU, so iteration is
* fine.
*/
spin_unlock_irq(&rq->lock);
move_task_off_dead_cpu(dead_cpu, p);
spin_lock_irq(&rq->lock);
put_task_struct(p);
}
/* release_task() removes task from tasklist, so we won't find dead tasks. */
static void migrate_dead_tasks(unsigned int dead_cpu)
{
struct rq *rq = cpu_rq(dead_cpu);
unsigned int arr, i;
for (arr = 0; arr < 2; arr++) {
for (i = 0; i < MAX_PRIO; i++) {
struct list_head *list = &rq->arrays[arr].queue[i];
while (!list_empty(list))
migrate_dead(dead_cpu, list_entry(list->next,
struct task_struct, run_list));
}
}
}
#endif /* CONFIG_HOTPLUG_CPU */
/*
* migration_call - callback that gets triggered when a CPU is added.
* Here we can start up the necessary migration thread for the new CPU.
*/
static int __cpuinit
migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
struct task_struct *p;
int cpu = (long)hcpu;
unsigned long flags;
struct rq *rq;
switch (action) {
case CPU_UP_PREPARE:
p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
if (IS_ERR(p))
return NOTIFY_BAD;
p->flags |= PF_NOFREEZE;
kthread_bind(p, cpu);
/* Must be high prio: stop_machine expects to yield to it. */
rq = task_rq_lock(p, &flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
task_rq_unlock(rq, &flags);
cpu_rq(cpu)->migration_thread = p;
break;
case CPU_ONLINE:
/* Strictly unneccessary, as first user will wake it. */
wake_up_process(cpu_rq(cpu)->migration_thread);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
if (!cpu_rq(cpu)->migration_thread)
break;
/* Unbind it from offline cpu so it can run. Fall thru. */
kthread_bind(cpu_rq(cpu)->migration_thread,
any_online_cpu(cpu_online_map));
kthread_stop(cpu_rq(cpu)->migration_thread);
cpu_rq(cpu)->migration_thread = NULL;
break;
case CPU_DEAD:
migrate_live_tasks(cpu);
rq = cpu_rq(cpu);
kthread_stop(rq->migration_thread);
rq->migration_thread = NULL;
/* Idle task back to normal (off runqueue, low prio) */
rq = task_rq_lock(rq->idle, &flags);
deactivate_task(rq->idle, rq);
rq->idle->static_prio = MAX_PRIO;
__setscheduler(rq->idle, SCHED_NORMAL, 0);
migrate_dead_tasks(cpu);
task_rq_unlock(rq, &flags);
migrate_nr_uninterruptible(rq);
BUG_ON(rq->nr_running != 0);
/* No need to migrate the tasks: it was best-effort if
* they didn't do lock_cpu_hotplug(). Just wake up
* the requestors. */
spin_lock_irq(&rq->lock);
while (!list_empty(&rq->migration_queue)) {
struct migration_req *req;
req = list_entry(rq->migration_queue.next,
struct migration_req, list);
list_del_init(&req->list);
complete(&req->done);
}
spin_unlock_irq(&rq->lock);
break;
#endif
}
return NOTIFY_OK;
}
/* Register at highest priority so that task migration (migrate_all_tasks)
* happens before everything else.
*/
static struct notifier_block __cpuinitdata migration_notifier = {
.notifier_call = migration_call,
.priority = 10
};
int __init migration_init(void)
{
void *cpu = (void *)(long)smp_processor_id();
int err;
/* Start one for the boot CPU: */
err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
BUG_ON(err == NOTIFY_BAD);
migration_call(&migration_notifier, CPU_ONLINE, cpu);
register_cpu_notifier(&migration_notifier);
return 0;
}
#endif
#ifdef CONFIG_SMP
#undef SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
static void sched_domain_debug(struct sched_domain *sd, int cpu)
{
int level = 0;
if (!sd) {
printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
return;
}
printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
do {
int i;
char str[NR_CPUS];
struct sched_group *group = sd->groups;
cpumask_t groupmask;
cpumask_scnprintf(str, NR_CPUS, sd->span);
cpus_clear(groupmask);
printk(KERN_DEBUG);
for (i = 0; i < level + 1; i++)
printk(" ");
printk("domain %d: ", level);
if (!(sd->flags & SD_LOAD_BALANCE)) {
printk("does not load-balance\n");
if (sd->parent)
printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain has parent");
break;
}
printk("span %s\n", str);
if (!cpu_isset(cpu, sd->span))
printk(KERN_ERR "ERROR: domain->span does not contain CPU%d\n", cpu);
if (!cpu_isset(cpu, group->cpumask))
printk(KERN_ERR "ERROR: domain->groups does not contain CPU%d\n", cpu);
printk(KERN_DEBUG);
for (i = 0; i < level + 2; i++)
printk(" ");
printk("groups:");
do {
if (!group) {
printk("\n");
printk(KERN_ERR "ERROR: group is NULL\n");
break;
}
if (!group->cpu_power) {
printk("\n");
printk(KERN_ERR "ERROR: domain->cpu_power not set\n");
}
if (!cpus_weight(group->cpumask)) {
printk("\n");
printk(KERN_ERR "ERROR: empty group\n");
}
if (cpus_intersects(groupmask, group->cpumask)) {
printk("\n");
printk(KERN_ERR "ERROR: repeated CPUs\n");
}
cpus_or(groupmask, groupmask, group->cpumask);
cpumask_scnprintf(str, NR_CPUS, group->cpumask);
printk(" %s", str);
group = group->next;
} while (group != sd->groups);
printk("\n");
if (!cpus_equal(sd->span, groupmask))
printk(KERN_ERR "ERROR: groups don't span domain->span\n");
level++;
sd = sd->parent;
if (sd) {
if (!cpus_subset(groupmask, sd->span))
printk(KERN_ERR "ERROR: parent span is not a superset of domain->span\n");
}
} while (sd);
}
#else
# define sched_domain_debug(sd, cpu) do { } while (0)
#endif
static int sd_degenerate(struct sched_domain *sd)
{
if (cpus_weight(sd->span) == 1)
return 1;
/* Following flags need at least 2 groups */
if (sd->flags & (SD_LOAD_BALANCE |
SD_BALANCE_NEWIDLE |
SD_BALANCE_FORK |
SD_BALANCE_EXEC)) {
if (sd->groups != sd->groups->next)
return 0;
}
/* Following flags don't use groups */
if (sd->flags & (SD_WAKE_IDLE |
SD_WAKE_AFFINE |
SD_WAKE_BALANCE))
return 0;
return 1;
}
static int
sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
{
unsigned long cflags = sd->flags, pflags = parent->flags;
if (sd_degenerate(parent))
return 1;
if (!cpus_equal(sd->span, parent->span))
return 0;
/* Does parent contain flags not in child? */
/* WAKE_BALANCE is a subset of WAKE_AFFINE */
if (cflags & SD_WAKE_AFFINE)
pflags &= ~SD_WAKE_BALANCE;
/* Flags needing groups don't count if only 1 group in parent */
if (parent->groups == parent->groups->next) {
pflags &= ~(SD_LOAD_BALANCE |
SD_BALANCE_NEWIDLE |
SD_BALANCE_FORK |
SD_BALANCE_EXEC);
}
if (~cflags & pflags)
return 0;
return 1;
}
/*
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
static void cpu_attach_domain(struct sched_domain *sd, int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; tmp = tmp->parent) {
struct sched_domain *parent = tmp->parent;
if (!parent)
break;
if (sd_parent_degenerate(tmp, parent))
tmp->parent = parent->parent;
}
if (sd && sd_degenerate(sd))
sd = sd->parent;
sched_domain_debug(sd, cpu);
rcu_assign_pointer(rq->sd, sd);
}
/* cpus with isolated domains */
static cpumask_t __devinitdata cpu_isolated_map = CPU_MASK_NONE;
/* Setup the mask of cpus configured for isolated domains */
static int __init isolated_cpu_setup(char *str)
{
int ints[NR_CPUS], i;
str = get_options(str, ARRAY_SIZE(ints), ints);
cpus_clear(cpu_isolated_map);
for (i = 1; i <= ints[0]; i++)
if (ints[i] < NR_CPUS)
cpu_set(ints[i], cpu_isolated_map);
return 1;
}
__setup ("isolcpus=", isolated_cpu_setup);
/*
* init_sched_build_groups takes an array of groups, the cpumask we wish
* to span, and a pointer to a function which identifies what group a CPU
* belongs to. The return value of group_fn must be a valid index into the
* groups[] array, and must be >= 0 and < NR_CPUS (due to the fact that we
* keep track of groups covered with a cpumask_t).
*
* init_sched_build_groups will build a circular linked list of the groups
* covered by the given span, and will set each group's ->cpumask correctly,
* and ->cpu_power to 0.
*/
static void init_sched_build_groups(struct sched_group groups[], cpumask_t span,
int (*group_fn)(int cpu))
{
struct sched_group *first = NULL, *last = NULL;
cpumask_t covered = CPU_MASK_NONE;
int i;
for_each_cpu_mask(i, span) {
int group = group_fn(i);
struct sched_group *sg = &groups[group];
int j;
if (cpu_isset(i, covered))
continue;
sg->cpumask = CPU_MASK_NONE;
sg->cpu_power = 0;
for_each_cpu_mask(j, span) {
if (group_fn(j) != group)
continue;
cpu_set(j, covered);
cpu_set(j, sg->cpumask);
}
if (!first)
first = sg;
if (last)
last->next = sg;
last = sg;
}
last->next = first;
}
#define SD_NODES_PER_DOMAIN 16
/*
* Self-tuning task migration cost measurement between source and target CPUs.
*
* This is done by measuring the cost of manipulating buffers of varying
* sizes. For a given buffer-size here are the steps that are taken:
*
* 1) the source CPU reads+dirties a shared buffer
* 2) the target CPU reads+dirties the same shared buffer
*
* We measure how long they take, in the following 4 scenarios:
*
* - source: CPU1, target: CPU2 | cost1
* - source: CPU2, target: CPU1 | cost2
* - source: CPU1, target: CPU1 | cost3
* - source: CPU2, target: CPU2 | cost4
*
* We then calculate the cost3+cost4-cost1-cost2 difference - this is
* the cost of migration.
*
* We then start off from a small buffer-size and iterate up to larger
* buffer sizes, in 5% steps - measuring each buffer-size separately, and
* doing a maximum search for the cost. (The maximum cost for a migration
* normally occurs when the working set size is around the effective cache
* size.)
*/
#define SEARCH_SCOPE 2
#define MIN_CACHE_SIZE (64*1024U)
#define DEFAULT_CACHE_SIZE (5*1024*1024U)
#define ITERATIONS 1
#define SIZE_THRESH 130
#define COST_THRESH 130
/*
* The migration cost is a function of 'domain distance'. Domain
* distance is the number of steps a CPU has to iterate down its
* domain tree to share a domain with the other CPU. The farther
* two CPUs are from each other, the larger the distance gets.
*
* Note that we use the distance only to cache measurement results,
* the distance value is not used numerically otherwise. When two
* CPUs have the same distance it is assumed that the migration
* cost is the same. (this is a simplification but quite practical)
*/
#define MAX_DOMAIN_DISTANCE 32
static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] =
{ [ 0 ... MAX_DOMAIN_DISTANCE-1 ] =
/*
* Architectures may override the migration cost and thus avoid
* boot-time calibration. Unit is nanoseconds. Mostly useful for
* virtualized hardware:
*/
#ifdef CONFIG_DEFAULT_MIGRATION_COST
CONFIG_DEFAULT_MIGRATION_COST
#else
-1LL
#endif
};
/*
* Allow override of migration cost - in units of microseconds.
* E.g. migration_cost=1000,2000,3000 will set up a level-1 cost
* of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs:
*/
static int __init migration_cost_setup(char *str)
{
int ints[MAX_DOMAIN_DISTANCE+1], i;
str = get_options(str, ARRAY_SIZE(ints), ints);
printk("#ints: %d\n", ints[0]);
for (i = 1; i <= ints[0]; i++) {
migration_cost[i-1] = (unsigned long long)ints[i]*1000;
printk("migration_cost[%d]: %Ld\n", i-1, migration_cost[i-1]);
}
return 1;
}
__setup ("migration_cost=", migration_cost_setup);
/*
* Global multiplier (divisor) for migration-cutoff values,
* in percentiles. E.g. use a value of 150 to get 1.5 times
* longer cache-hot cutoff times.
*
* (We scale it from 100 to 128 to long long handling easier.)
*/
#define MIGRATION_FACTOR_SCALE 128
static unsigned int migration_factor = MIGRATION_FACTOR_SCALE;
static int __init setup_migration_factor(char *str)
{
get_option(&str, &migration_factor);
migration_factor = migration_factor * MIGRATION_FACTOR_SCALE / 100;
return 1;
}
__setup("migration_factor=", setup_migration_factor);
/*
* Estimated distance of two CPUs, measured via the number of domains
* we have to pass for the two CPUs to be in the same span:
*/
static unsigned long domain_distance(int cpu1, int cpu2)
{
unsigned long distance = 0;
struct sched_domain *sd;
for_each_domain(cpu1, sd) {
WARN_ON(!cpu_isset(cpu1, sd->span));
if (cpu_isset(cpu2, sd->span))
return distance;
distance++;
}
if (distance >= MAX_DOMAIN_DISTANCE) {
WARN_ON(1);
distance = MAX_DOMAIN_DISTANCE-1;
}
return distance;
}
static unsigned int migration_debug;
static int __init setup_migration_debug(char *str)
{
get_option(&str, &migration_debug);
return 1;
}
__setup("migration_debug=", setup_migration_debug);
/*
* Maximum cache-size that the scheduler should try to measure.
* Architectures with larger caches should tune this up during
* bootup. Gets used in the domain-setup code (i.e. during SMP
* bootup).
*/
unsigned int max_cache_size;
static int __init setup_max_cache_size(char *str)
{
get_option(&str, &max_cache_size);
return 1;
}
__setup("max_cache_size=", setup_max_cache_size);
/*
* Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This
* is the operation that is timed, so we try to generate unpredictable
* cachemisses that still end up filling the L2 cache:
*/
static void touch_cache(void *__cache, unsigned long __size)
{
unsigned long size = __size/sizeof(long), chunk1 = size/3,
chunk2 = 2*size/3;
unsigned long *cache = __cache;
int i;
for (i = 0; i < size/6; i += 8) {
switch (i % 6) {
case 0: cache[i]++;
case 1: cache[size-1-i]++;
case 2: cache[chunk1-i]++;
case 3: cache[chunk1+i]++;
case 4: cache[chunk2-i]++;
case 5: cache[chunk2+i]++;
}
}
}
/*
* Measure the cache-cost of one task migration. Returns in units of nsec.
*/
static unsigned long long
measure_one(void *cache, unsigned long size, int source, int target)
{
cpumask_t mask, saved_mask;
unsigned long long t0, t1, t2, t3, cost;
saved_mask = current->cpus_allowed;
/*
* Flush source caches to RAM and invalidate them:
*/
sched_cacheflush();
/*
* Migrate to the source CPU:
*/
mask = cpumask_of_cpu(source);
set_cpus_allowed(current, mask);
WARN_ON(smp_processor_id() != source);
/*
* Dirty the working set:
*/
t0 = sched_clock();
touch_cache(cache, size);
t1 = sched_clock();
/*
* Migrate to the target CPU, dirty the L2 cache and access
* the shared buffer. (which represents the working set
* of a migrated task.)
*/
mask = cpumask_of_cpu(target);
set_cpus_allowed(current, mask);
WARN_ON(smp_processor_id() != target);
t2 = sched_clock();
touch_cache(cache, size);
t3 = sched_clock();
cost = t1-t0 + t3-t2;
if (migration_debug >= 2)
printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n",
source, target, t1-t0, t1-t0, t3-t2, cost);
/*
* Flush target caches to RAM and invalidate them:
*/
sched_cacheflush();
set_cpus_allowed(current, saved_mask);
return cost;
}
/*
* Measure a series of task migrations and return the average
* result. Since this code runs early during bootup the system
* is 'undisturbed' and the average latency makes sense.
*
* The algorithm in essence auto-detects the relevant cache-size,
* so it will properly detect different cachesizes for different
* cache-hierarchies, depending on how the CPUs are connected.
*
* Architectures can prime the upper limit of the search range via
* max_cache_size, otherwise the search range defaults to 20MB...64K.
*/
static unsigned long long
measure_cost(int cpu1, int cpu2, void *cache, unsigned int size)
{
unsigned long long cost1, cost2;
int i;
/*
* Measure the migration cost of 'size' bytes, over an
* average of 10 runs:
*
* (We perturb the cache size by a small (0..4k)
* value to compensate size/alignment related artifacts.
* We also subtract the cost of the operation done on
* the same CPU.)
*/
cost1 = 0;
/*
* dry run, to make sure we start off cache-cold on cpu1,
* and to get any vmalloc pagefaults in advance:
*/
measure_one(cache, size, cpu1, cpu2);
for (i = 0; i < ITERATIONS; i++)
cost1 += measure_one(cache, size - i*1024, cpu1, cpu2);
measure_one(cache, size, cpu2, cpu1);
for (i = 0; i < ITERATIONS; i++)
cost1 += measure_one(cache, size - i*1024, cpu2, cpu1);
/*
* (We measure the non-migrating [cached] cost on both
* cpu1 and cpu2, to handle CPUs with different speeds)
*/
cost2 = 0;
measure_one(cache, size, cpu1, cpu1);
for (i = 0; i < ITERATIONS; i++)
cost2 += measure_one(cache, size - i*1024, cpu1, cpu1);
measure_one(cache, size, cpu2, cpu2);
for (i = 0; i < ITERATIONS; i++)
cost2 += measure_one(cache, size - i*1024, cpu2, cpu2);
/*
* Get the per-iteration migration cost:
*/
do_div(cost1, 2*ITERATIONS);
do_div(cost2, 2*ITERATIONS);
return cost1 - cost2;
}
static unsigned long long measure_migration_cost(int cpu1, int cpu2)
{
unsigned long long max_cost = 0, fluct = 0, avg_fluct = 0;
unsigned int max_size, size, size_found = 0;
long long cost = 0, prev_cost;
void *cache;
/*
* Search from max_cache_size*5 down to 64K - the real relevant
* cachesize has to lie somewhere inbetween.
*/
if (max_cache_size) {
max_size = max(max_cache_size * SEARCH_SCOPE, MIN_CACHE_SIZE);
size = max(max_cache_size / SEARCH_SCOPE, MIN_CACHE_SIZE);
} else {
/*
* Since we have no estimation about the relevant
* search range
*/
max_size = DEFAULT_CACHE_SIZE * SEARCH_SCOPE;
size = MIN_CACHE_SIZE;
}
if (!cpu_online(cpu1) || !cpu_online(cpu2)) {
printk("cpu %d and %d not both online!\n", cpu1, cpu2);
return 0;
}
/*
* Allocate the working set:
*/
cache = vmalloc(max_size);
if (!cache) {
printk("could not vmalloc %d bytes for cache!\n", 2*max_size);
return 1000000; /* return 1 msec on very small boxen */
}
while (size <= max_size) {
prev_cost = cost;
cost = measure_cost(cpu1, cpu2, cache, size);
/*
* Update the max:
*/
if (cost > 0) {
if (max_cost < cost) {
max_cost = cost;
size_found = size;
}
}
/*
* Calculate average fluctuation, we use this to prevent
* noise from triggering an early break out of the loop:
*/
fluct = abs(cost - prev_cost);
avg_fluct = (avg_fluct + fluct)/2;
if (migration_debug)
printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): (%8Ld %8Ld)\n",
cpu1, cpu2, size,
(long)cost / 1000000,
((long)cost / 100000) % 10,
(long)max_cost / 1000000,
((long)max_cost / 100000) % 10,
domain_distance(cpu1, cpu2),
cost, avg_fluct);
/*
* If we iterated at least 20% past the previous maximum,
* and the cost has dropped by more than 20% already,
* (taking fluctuations into account) then we assume to
* have found the maximum and break out of the loop early:
*/
if (size_found && (size*100 > size_found*SIZE_THRESH))
if (cost+avg_fluct <= 0 ||
max_cost*100 > (cost+avg_fluct)*COST_THRESH) {
if (migration_debug)
printk("-> found max.\n");
break;
}
/*
* Increase the cachesize in 10% steps:
*/
size = size * 10 / 9;
}
if (migration_debug)
printk("[%d][%d] working set size found: %d, cost: %Ld\n",
cpu1, cpu2, size_found, max_cost);
vfree(cache);
/*
* A task is considered 'cache cold' if at least 2 times
* the worst-case cost of migration has passed.
*
* (this limit is only listened to if the load-balancing
* situation is 'nice' - if there is a large imbalance we
* ignore it for the sake of CPU utilization and
* processing fairness.)
*/
return 2 * max_cost * migration_factor / MIGRATION_FACTOR_SCALE;
}
static void calibrate_migration_costs(const cpumask_t *cpu_map)
{
int cpu1 = -1, cpu2 = -1, cpu, orig_cpu = raw_smp_processor_id();
unsigned long j0, j1, distance, max_distance = 0;
struct sched_domain *sd;
j0 = jiffies;
/*
* First pass - calculate the cacheflush times:
*/
for_each_cpu_mask(cpu1, *cpu_map) {
for_each_cpu_mask(cpu2, *cpu_map) {
if (cpu1 == cpu2)
continue;
distance = domain_distance(cpu1, cpu2);
max_distance = max(max_distance, distance);
/*
* No result cached yet?
*/
if (migration_cost[distance] == -1LL)
migration_cost[distance] =
measure_migration_cost(cpu1, cpu2);
}
}
/*
* Second pass - update the sched domain hierarchy with
* the new cache-hot-time estimations:
*/
for_each_cpu_mask(cpu, *cpu_map) {
distance = 0;
for_each_domain(cpu, sd) {
sd->cache_hot_time = migration_cost[distance];
distance++;
}
}
/*
* Print the matrix:
*/
if (migration_debug)
printk("migration: max_cache_size: %d, cpu: %d MHz:\n",
max_cache_size,
#ifdef CONFIG_X86
cpu_khz/1000
#else
-1
#endif
);
if (system_state == SYSTEM_BOOTING) {
printk("migration_cost=");
for (distance = 0; distance <= max_distance; distance++) {
if (distance)
printk(",");
printk("%ld", (long)migration_cost[distance] / 1000);
}
printk("\n");
}
j1 = jiffies;
if (migration_debug)
printk("migration: %ld seconds\n", (j1-j0)/HZ);
/*
* Move back to the original CPU. NUMA-Q gets confused
* if we migrate to another quad during bootup.
*/
if (raw_smp_processor_id() != orig_cpu) {
cpumask_t mask = cpumask_of_cpu(orig_cpu),
saved_mask = current->cpus_allowed;
set_cpus_allowed(current, mask);
set_cpus_allowed(current, saved_mask);
}
}
#ifdef CONFIG_NUMA
/**
* find_next_best_node - find the next node to include in a sched_domain
* @node: node whose sched_domain we're building
* @used_nodes: nodes already in the sched_domain
*
* Find the next node to include in a given scheduling domain. Simply
* finds the closest node not already in the @used_nodes map.
*
* Should use nodemask_t.
*/
static int find_next_best_node(int node, unsigned long *used_nodes)
{
int i, n, val, min_val, best_node = 0;
min_val = INT_MAX;
for (i = 0; i < MAX_NUMNODES; i++) {
/* Start at @node */
n = (node + i) % MAX_NUMNODES;
if (!nr_cpus_node(n))
continue;
/* Skip already used nodes */
if (test_bit(n, used_nodes))
continue;
/* Simple min distance search */
val = node_distance(node, n);
if (val < min_val) {
min_val = val;
best_node = n;
}
}
set_bit(best_node, used_nodes);
return best_node;
}
/**
* sched_domain_node_span - get a cpumask for a node's sched_domain
* @node: node whose cpumask we're constructing
* @size: number of nodes to include in this span
*
* Given a node, construct a good cpumask for its sched_domain to span. It
* should be one that prevents unnecessary balancing, but also spreads tasks
* out optimally.
*/
static cpumask_t sched_domain_node_span(int node)
{
DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
cpumask_t span, nodemask;
int i;
cpus_clear(span);
bitmap_zero(used_nodes, MAX_NUMNODES);
nodemask = node_to_cpumask(node);
cpus_or(span, span, nodemask);
set_bit(node, used_nodes);
for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
int next_node = find_next_best_node(node, used_nodes);
nodemask = node_to_cpumask(next_node);
cpus_or(span, span, nodemask);
}
return span;
}
#endif
int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
/*
* SMT sched-domains:
*/
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static struct sched_group sched_group_cpus[NR_CPUS];
static int cpu_to_cpu_group(int cpu)
{
return cpu;
}
#endif
/*
* multi-core sched-domains:
*/
#ifdef CONFIG_SCHED_MC
static DEFINE_PER_CPU(struct sched_domain, core_domains);
static struct sched_group *sched_group_core_bycpu[NR_CPUS];
#endif
#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
static int cpu_to_core_group(int cpu)
{
return first_cpu(cpu_sibling_map[cpu]);
}
#elif defined(CONFIG_SCHED_MC)
static int cpu_to_core_group(int cpu)
{
return cpu;
}
#endif
static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static struct sched_group *sched_group_phys_bycpu[NR_CPUS];
static int cpu_to_phys_group(int cpu)
{
#ifdef CONFIG_SCHED_MC
cpumask_t mask = cpu_coregroup_map(cpu);
return first_cpu(mask);
#elif defined(CONFIG_SCHED_SMT)
return first_cpu(cpu_sibling_map[cpu]);
#else
return cpu;
#endif
}
#ifdef CONFIG_NUMA
/*
* The init_sched_build_groups can't handle what we want to do with node
* groups, so roll our own. Now each node has its own list of groups which
* gets dynamically allocated.
*/
static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];
static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
static struct sched_group *sched_group_allnodes_bycpu[NR_CPUS];
static int cpu_to_allnodes_group(int cpu)
{
return cpu_to_node(cpu);
}
static void init_numa_sched_groups_power(struct sched_group *group_head)
{
struct sched_group *sg = group_head;
int j;
if (!sg)
return;
next_sg:
for_each_cpu_mask(j, sg->cpumask) {
struct sched_domain *sd;
sd = &per_cpu(phys_domains, j);
if (j != first_cpu(sd->groups->cpumask)) {
/*
* Only add "power" once for each
* physical package.
*/
continue;
}
sg->cpu_power += sd->groups->cpu_power;
}
sg = sg->next;
if (sg != group_head)
goto next_sg;
}
#endif
/* Free memory allocated for various sched_group structures */
static void free_sched_groups(const cpumask_t *cpu_map)
{
int cpu;
#ifdef CONFIG_NUMA
int i;
for_each_cpu_mask(cpu, *cpu_map) {
struct sched_group *sched_group_allnodes
= sched_group_allnodes_bycpu[cpu];
struct sched_group **sched_group_nodes
= sched_group_nodes_bycpu[cpu];
if (sched_group_allnodes) {
kfree(sched_group_allnodes);
sched_group_allnodes_bycpu[cpu] = NULL;
}
if (!sched_group_nodes)
continue;
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);
struct sched_group *oldsg, *sg = sched_group_nodes[i];
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask))
continue;
if (sg == NULL)
continue;
sg = sg->next;
next_sg:
oldsg = sg;
sg = sg->next;
kfree(oldsg);
if (oldsg != sched_group_nodes[i])
goto next_sg;
}
kfree(sched_group_nodes);
sched_group_nodes_bycpu[cpu] = NULL;
}
#endif
for_each_cpu_mask(cpu, *cpu_map) {
if (sched_group_phys_bycpu[cpu]) {
kfree(sched_group_phys_bycpu[cpu]);
sched_group_phys_bycpu[cpu] = NULL;
}
#ifdef CONFIG_SCHED_MC
if (sched_group_core_bycpu[cpu]) {
kfree(sched_group_core_bycpu[cpu]);
sched_group_core_bycpu[cpu] = NULL;
}
#endif
}
}
/*
* Build sched domains for a given set of cpus and attach the sched domains
* to the individual cpus
*/
static int build_sched_domains(const cpumask_t *cpu_map)
{
int i;
struct sched_group *sched_group_phys = NULL;
#ifdef CONFIG_SCHED_MC
struct sched_group *sched_group_core = NULL;
#endif
#ifdef CONFIG_NUMA
struct sched_group **sched_group_nodes = NULL;
struct sched_group *sched_group_allnodes = NULL;
/*
* Allocate the per-node list of sched groups
*/
sched_group_nodes = kzalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
GFP_KERNEL);
if (!sched_group_nodes) {
printk(KERN_WARNING "Can not alloc sched group node list\n");
return -ENOMEM;
}
sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
#endif
/*
* Set up domains for cpus specified by the cpu_map.
*/
for_each_cpu_mask(i, *cpu_map) {
int group;
struct sched_domain *sd = NULL, *p;
cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));
cpus_and(nodemask, nodemask, *cpu_map);
#ifdef CONFIG_NUMA
if (cpus_weight(*cpu_map)
> SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
if (!sched_group_allnodes) {
sched_group_allnodes
= kmalloc(sizeof(struct sched_group)
* MAX_NUMNODES,
GFP_KERNEL);
if (!sched_group_allnodes) {
printk(KERN_WARNING
"Can not alloc allnodes sched group\n");
goto error;
}
sched_group_allnodes_bycpu[i]
= sched_group_allnodes;
}
sd = &per_cpu(allnodes_domains, i);
*sd = SD_ALLNODES_INIT;
sd->span = *cpu_map;
group = cpu_to_allnodes_group(i);
sd->groups = &sched_group_allnodes[group];
p = sd;
} else
p = NULL;
sd = &per_cpu(node_domains, i);
*sd = SD_NODE_INIT;
sd->span = sched_domain_node_span(cpu_to_node(i));
sd->parent = p;
cpus_and(sd->span, sd->span, *cpu_map);
#endif
if (!sched_group_phys) {
sched_group_phys
= kmalloc(sizeof(struct sched_group) * NR_CPUS,
GFP_KERNEL);
if (!sched_group_phys) {
printk (KERN_WARNING "Can not alloc phys sched"
"group\n");
goto error;
}
sched_group_phys_bycpu[i] = sched_group_phys;
}
p = sd;
sd = &per_cpu(phys_domains, i);
group = cpu_to_phys_group(i);
*sd = SD_CPU_INIT;
sd->span = nodemask;
sd->parent = p;
sd->groups = &sched_group_phys[group];
#ifdef CONFIG_SCHED_MC
if (!sched_group_core) {
sched_group_core
= kmalloc(sizeof(struct sched_group) * NR_CPUS,
GFP_KERNEL);
if (!sched_group_core) {
printk (KERN_WARNING "Can not alloc core sched"
"group\n");
goto error;
}
sched_group_core_bycpu[i] = sched_group_core;
}
p = sd;
sd = &per_cpu(core_domains, i);
group = cpu_to_core_group(i);
*sd = SD_MC_INIT;
sd->span = cpu_coregroup_map(i);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
sd->groups = &sched_group_core[group];
#endif
#ifdef CONFIG_SCHED_SMT
p = sd;
sd = &per_cpu(cpu_domains, i);
group = cpu_to_cpu_group(i);
*sd = SD_SIBLING_INIT;
sd->span = cpu_sibling_map[i];
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
sd->groups = &sched_group_cpus[group];
#endif
}
#ifdef CONFIG_SCHED_SMT
/* Set up CPU (sibling) groups */
for_each_cpu_mask(i, *cpu_map) {
cpumask_t this_sibling_map = cpu_sibling_map[i];
cpus_and(this_sibling_map, this_sibling_map, *cpu_map);
if (i != first_cpu(this_sibling_map))
continue;
init_sched_build_groups(sched_group_cpus, this_sibling_map,
&cpu_to_cpu_group);
}
#endif
#ifdef CONFIG_SCHED_MC
/* Set up multi-core groups */
for_each_cpu_mask(i, *cpu_map) {
cpumask_t this_core_map = cpu_coregroup_map(i);
cpus_and(this_core_map, this_core_map, *cpu_map);
if (i != first_cpu(this_core_map))
continue;
init_sched_build_groups(sched_group_core, this_core_map,
&cpu_to_core_group);
}
#endif
/* Set up physical groups */
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask))
continue;
init_sched_build_groups(sched_group_phys, nodemask,
&cpu_to_phys_group);
}
#ifdef CONFIG_NUMA
/* Set up node groups */
if (sched_group_allnodes)
init_sched_build_groups(sched_group_allnodes, *cpu_map,
&cpu_to_allnodes_group);
for (i = 0; i < MAX_NUMNODES; i++) {
/* Set up node groups */
struct sched_group *sg, *prev;
cpumask_t nodemask = node_to_cpumask(i);
cpumask_t domainspan;
cpumask_t covered = CPU_MASK_NONE;
int j;
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask)) {
sched_group_nodes[i] = NULL;
continue;
}
domainspan = sched_domain_node_span(i);
cpus_and(domainspan, domainspan, *cpu_map);
sg = kmalloc_node(sizeof(struct sched_group), GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING "Can not alloc domain group for "
"node %d\n", i);
goto error;
}
sched_group_nodes[i] = sg;
for_each_cpu_mask(j, nodemask) {
struct sched_domain *sd;
sd = &per_cpu(node_domains, j);
sd->groups = sg;
}
sg->cpu_power = 0;
sg->cpumask = nodemask;
sg->next = sg;
cpus_or(covered, covered, nodemask);
prev = sg;
for (j = 0; j < MAX_NUMNODES; j++) {
cpumask_t tmp, notcovered;
int n = (i + j) % MAX_NUMNODES;
cpus_complement(notcovered, covered);
cpus_and(tmp, notcovered, *cpu_map);
cpus_and(tmp, tmp, domainspan);
if (cpus_empty(tmp))
break;
nodemask = node_to_cpumask(n);
cpus_and(tmp, tmp, nodemask);
if (cpus_empty(tmp))
continue;
sg = kmalloc_node(sizeof(struct sched_group),
GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING
"Can not alloc domain group for node %d\n", j);
goto error;
}
sg->cpu_power = 0;
sg->cpumask = tmp;
sg->next = prev->next;
cpus_or(covered, covered, tmp);
prev->next = sg;
prev = sg;
}
}
#endif
/* Calculate CPU power for physical packages and nodes */
#ifdef CONFIG_SCHED_SMT
for_each_cpu_mask(i, *cpu_map) {
struct sched_domain *sd;
sd = &per_cpu(cpu_domains, i);
sd->groups->cpu_power = SCHED_LOAD_SCALE;
}
#endif
#ifdef CONFIG_SCHED_MC
for_each_cpu_mask(i, *cpu_map) {
int power;
struct sched_domain *sd;
sd = &per_cpu(core_domains, i);
if (sched_smt_power_savings)
power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
else
power = SCHED_LOAD_SCALE + (cpus_weight(sd->groups->cpumask)-1)
* SCHED_LOAD_SCALE / 10;
sd->groups->cpu_power = power;
}
#endif
for_each_cpu_mask(i, *cpu_map) {
struct sched_domain *sd;
#ifdef CONFIG_SCHED_MC
sd = &per_cpu(phys_domains, i);
if (i != first_cpu(sd->groups->cpumask))
continue;
sd->groups->cpu_power = 0;
if (sched_mc_power_savings || sched_smt_power_savings) {
int j;
for_each_cpu_mask(j, sd->groups->cpumask) {
struct sched_domain *sd1;
sd1 = &per_cpu(core_domains, j);
/*
* for each core we will add once
* to the group in physical domain
*/
if (j != first_cpu(sd1->groups->cpumask))
continue;
if (sched_smt_power_savings)
sd->groups->cpu_power += sd1->groups->cpu_power;
else
sd->groups->cpu_power += SCHED_LOAD_SCALE;
}
} else
/*
* This has to be < 2 * SCHED_LOAD_SCALE
* Lets keep it SCHED_LOAD_SCALE, so that
* while calculating NUMA group's cpu_power
* we can simply do
* numa_group->cpu_power += phys_group->cpu_power;
*
* See "only add power once for each physical pkg"
* comment below
*/
sd->groups->cpu_power = SCHED_LOAD_SCALE;
#else
int power;
sd = &per_cpu(phys_domains, i);
if (sched_smt_power_savings)
power = SCHED_LOAD_SCALE * cpus_weight(sd->groups->cpumask);
else
power = SCHED_LOAD_SCALE;
sd->groups->cpu_power = power;
#endif
}
#ifdef CONFIG_NUMA
for (i = 0; i < MAX_NUMNODES; i++)
init_numa_sched_groups_power(sched_group_nodes[i]);
if (sched_group_allnodes) {
int group = cpu_to_allnodes_group(first_cpu(*cpu_map));
struct sched_group *sg = &sched_group_allnodes[group];
init_numa_sched_groups_power(sg);
}
#endif
/* Attach the domains */
for_each_cpu_mask(i, *cpu_map) {
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
#elif defined(CONFIG_SCHED_MC)
sd = &per_cpu(core_domains, i);
#else
sd = &per_cpu(phys_domains, i);
#endif
cpu_attach_domain(sd, i);
}
/*
* Tune cache-hot values:
*/
calibrate_migration_costs(cpu_map);
return 0;
error:
free_sched_groups(cpu_map);
return -ENOMEM;
}
/*
* Set up scheduler domains and groups. Callers must hold the hotplug lock.
*/
static int arch_init_sched_domains(const cpumask_t *cpu_map)
{
cpumask_t cpu_default_map;
int err;
/*
* Setup mask for cpus without special case scheduling requirements.
* For now this just excludes isolated cpus, but could be used to
* exclude other special cases in the future.
*/
cpus_andnot(cpu_default_map, *cpu_map, cpu_isolated_map);
err = build_sched_domains(&cpu_default_map);
return err;
}
static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
{
free_sched_groups(cpu_map);
}
/*
* Detach sched domains from a group of cpus specified in cpu_map
* These cpus will now be attached to the NULL domain
*/
static void detach_destroy_domains(const cpumask_t *cpu_map)
{
int i;
for_each_cpu_mask(i, *cpu_map)
cpu_attach_domain(NULL, i);
synchronize_sched();
arch_destroy_sched_domains(cpu_map);
}
/*
* Partition sched domains as specified by the cpumasks below.
* This attaches all cpus from the cpumasks to the NULL domain,
* waits for a RCU quiescent period, recalculates sched
* domain information and then attaches them back to the
* correct sched domains
* Call with hotplug lock held
*/
int partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
{
cpumask_t change_map;
int err = 0;
cpus_and(*partition1, *partition1, cpu_online_map);
cpus_and(*partition2, *partition2, cpu_online_map);
cpus_or(change_map, *partition1, *partition2);
/* Detach sched domains from all of the affected cpus */
detach_destroy_domains(&change_map);
if (!cpus_empty(*partition1))
err = build_sched_domains(partition1);
if (!err && !cpus_empty(*partition2))
err = build_sched_domains(partition2);
return err;
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
int arch_reinit_sched_domains(void)
{
int err;
lock_cpu_hotplug();
detach_destroy_domains(&cpu_online_map);
err = arch_init_sched_domains(&cpu_online_map);
unlock_cpu_hotplug();
return err;
}
static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
{
int ret;
if (buf[0] != '0' && buf[0] != '1')
return -EINVAL;
if (smt)
sched_smt_power_savings = (buf[0] == '1');
else
sched_mc_power_savings = (buf[0] == '1');
ret = arch_reinit_sched_domains();
return ret ? ret : count;
}
int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
{
int err = 0;
#ifdef CONFIG_SCHED_SMT
if (smt_capable())
err = sysfs_create_file(&cls->kset.kobj,
&attr_sched_smt_power_savings.attr);
#endif
#ifdef CONFIG_SCHED_MC
if (!err && mc_capable())
err = sysfs_create_file(&cls->kset.kobj,
&attr_sched_mc_power_savings.attr);
#endif
return err;
}
#endif
#ifdef CONFIG_SCHED_MC
static ssize_t sched_mc_power_savings_show(struct sys_device *dev, char *page)
{
return sprintf(page, "%u\n", sched_mc_power_savings);
}
static ssize_t sched_mc_power_savings_store(struct sys_device *dev,
const char *buf, size_t count)
{
return sched_power_savings_store(buf, count, 0);
}
SYSDEV_ATTR(sched_mc_power_savings, 0644, sched_mc_power_savings_show,
sched_mc_power_savings_store);
#endif
#ifdef CONFIG_SCHED_SMT
static ssize_t sched_smt_power_savings_show(struct sys_device *dev, char *page)
{
return sprintf(page, "%u\n", sched_smt_power_savings);
}
static ssize_t sched_smt_power_savings_store(struct sys_device *dev,
const char *buf, size_t count)
{
return sched_power_savings_store(buf, count, 1);
}
SYSDEV_ATTR(sched_smt_power_savings, 0644, sched_smt_power_savings_show,
sched_smt_power_savings_store);
#endif
#ifdef CONFIG_HOTPLUG_CPU
/*
* Force a reinitialization of the sched domains hierarchy. The domains
* and groups cannot be updated in place without racing with the balancing
* code, so we temporarily attach all running cpus to the NULL domain
* which will prevent rebalancing while the sched domains are recalculated.
*/
static int update_sched_domains(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action) {
case CPU_UP_PREPARE:
case CPU_DOWN_PREPARE:
detach_destroy_domains(&cpu_online_map);
return NOTIFY_OK;
case CPU_UP_CANCELED:
case CPU_DOWN_FAILED:
case CPU_ONLINE:
case CPU_DEAD:
/*
* Fall through and re-initialise the domains.
*/
break;
default:
return NOTIFY_DONE;
}
/* The hotplug lock is already held by cpu_up/cpu_down */
arch_init_sched_domains(&cpu_online_map);
return NOTIFY_OK;
}
#endif
void __init sched_init_smp(void)
{
lock_cpu_hotplug();
arch_init_sched_domains(&cpu_online_map);
unlock_cpu_hotplug();
/* XXX: Theoretical race here - CPU may be hotplugged now */
hotcpu_notifier(update_sched_domains, 0);
}
#else
void __init sched_init_smp(void)
{
}
#endif /* CONFIG_SMP */
int in_sched_functions(unsigned long addr)
{
/* Linker adds these: start and end of __sched functions */
extern char __sched_text_start[], __sched_text_end[];
return in_lock_functions(addr) ||
(addr >= (unsigned long)__sched_text_start
&& addr < (unsigned long)__sched_text_end);
}
void __init sched_init(void)
{
int i, j, k;
for_each_possible_cpu(i) {
struct prio_array *array;
struct rq *rq;
rq = cpu_rq(i);
spin_lock_init(&rq->lock);
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
rq->best_expired_prio = MAX_PRIO;
#ifdef CONFIG_SMP
rq->sd = NULL;
for (j = 1; j < 3; j++)
rq->cpu_load[j] = 0;
rq->active_balance = 0;
rq->push_cpu = 0;
rq->cpu = i;
rq->migration_thread = NULL;
INIT_LIST_HEAD(&rq->migration_queue);
#endif
atomic_set(&rq->nr_iowait, 0);
for (j = 0; j < 2; j++) {
array = rq->arrays + j;
for (k = 0; k < MAX_PRIO; k++) {
INIT_LIST_HEAD(array->queue + k);
__clear_bit(k, array->bitmap);
}
// delimiter for bitsearch
__set_bit(MAX_PRIO, array->bitmap);
}
}
set_load_weight(&init_task);
#ifdef CONFIG_RT_MUTEXES
plist_head_init(&init_task.pi_waiters, &init_task.pi_lock);
#endif
/*
* The boot idle thread does lazy MMU switching as well:
*/
atomic_inc(&init_mm.mm_count);
enter_lazy_tlb(&init_mm, current);
/*
* Make us the idle thread. Technically, schedule() should not be
* called from this thread, however somewhere below it might be,
* but because we are the idle thread, we just pick up running again
* when this runqueue becomes "idle".
*/
init_idle(current, smp_processor_id());
}
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
void __might_sleep(char *file, int line)
{
#ifdef in_atomic
static unsigned long prev_jiffy; /* ratelimiting */
if ((in_atomic() || irqs_disabled()) &&
system_state == SYSTEM_RUNNING && !oops_in_progress) {
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
printk(KERN_ERR "BUG: sleeping function called from invalid"
" context at %s:%d\n", file, line);
printk("in_atomic():%d, irqs_disabled():%d\n",
in_atomic(), irqs_disabled());
dump_stack();
}
#endif
}
EXPORT_SYMBOL(__might_sleep);
#endif
#ifdef CONFIG_MAGIC_SYSRQ
void normalize_rt_tasks(void)
{
struct prio_array *array;
struct task_struct *p;
unsigned long flags;
struct rq *rq;
read_lock_irq(&tasklist_lock);
for_each_process(p) {
if (!rt_task(p))
continue;
spin_lock_irqsave(&p->pi_lock, flags);
rq = __task_rq_lock(p);
array = p->array;
if (array)
deactivate_task(p, task_rq(p));
__setscheduler(p, SCHED_NORMAL, 0);
if (array) {
__activate_task(p, task_rq(p));
resched_task(rq->curr);
}
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
}
read_unlock_irq(&tasklist_lock);
}
#endif /* CONFIG_MAGIC_SYSRQ */
#ifdef CONFIG_IA64
/*
* These functions are only useful for the IA64 MCA handling.
*
* They can only be called when the whole system has been
* stopped - every CPU needs to be quiescent, and no scheduling
* activity can take place. Using them for anything else would
* be a serious bug, and as a result, they aren't even visible
* under any other configuration.
*/
/**
* curr_task - return the current task for a given cpu.
* @cpu: the processor in question.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*/
struct task_struct *curr_task(int cpu)
{
return cpu_curr(cpu);
}
/**
* set_curr_task - set the current task for a given cpu.
* @cpu: the processor in question.
* @p: the task pointer to set.
*
* Description: This function must only be used when non-maskable interrupts
* are serviced on a separate stack. It allows the architecture to switch the
* notion of the current task on a cpu in a non-blocking manner. This function
* must be called with all CPU's synchronized, and interrupts disabled, the
* and caller must save the original value of the current task (see
* curr_task() above) and restore that value before reenabling interrupts and
* re-starting the system.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*/
void set_curr_task(int cpu, struct task_struct *p)
{
cpu_curr(cpu) = p;
}
#endif
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