fa4062e7ea
kernel_lock.c emits a warning because a raw spinlock function is used with a spinlock. Convert BKL to raw_spinlock. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra <peterz@infradead.org> Acked-by: Ingo Molnar <mingo@elte.hu>
143 lines
3.2 KiB
C
143 lines
3.2 KiB
C
/*
|
|
* lib/kernel_lock.c
|
|
*
|
|
* This is the traditional BKL - big kernel lock. Largely
|
|
* relegated to obsolescence, but used by various less
|
|
* important (or lazy) subsystems.
|
|
*/
|
|
#include <linux/module.h>
|
|
#include <linux/kallsyms.h>
|
|
#include <linux/semaphore.h>
|
|
#include <linux/smp_lock.h>
|
|
|
|
#define CREATE_TRACE_POINTS
|
|
#include <trace/events/bkl.h>
|
|
|
|
/*
|
|
* The 'big kernel lock'
|
|
*
|
|
* This spinlock is taken and released recursively by lock_kernel()
|
|
* and unlock_kernel(). It is transparently dropped and reacquired
|
|
* over schedule(). It is used to protect legacy code that hasn't
|
|
* been migrated to a proper locking design yet.
|
|
*
|
|
* Don't use in new code.
|
|
*/
|
|
static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(kernel_flag);
|
|
|
|
|
|
/*
|
|
* Acquire/release the underlying lock from the scheduler.
|
|
*
|
|
* This is called with preemption disabled, and should
|
|
* return an error value if it cannot get the lock and
|
|
* TIF_NEED_RESCHED gets set.
|
|
*
|
|
* If it successfully gets the lock, it should increment
|
|
* the preemption count like any spinlock does.
|
|
*
|
|
* (This works on UP too - do_raw_spin_trylock will never
|
|
* return false in that case)
|
|
*/
|
|
int __lockfunc __reacquire_kernel_lock(void)
|
|
{
|
|
while (!do_raw_spin_trylock(&kernel_flag)) {
|
|
if (need_resched())
|
|
return -EAGAIN;
|
|
cpu_relax();
|
|
}
|
|
preempt_disable();
|
|
return 0;
|
|
}
|
|
|
|
void __lockfunc __release_kernel_lock(void)
|
|
{
|
|
do_raw_spin_unlock(&kernel_flag);
|
|
preempt_enable_no_resched();
|
|
}
|
|
|
|
/*
|
|
* These are the BKL spinlocks - we try to be polite about preemption.
|
|
* If SMP is not on (ie UP preemption), this all goes away because the
|
|
* do_raw_spin_trylock() will always succeed.
|
|
*/
|
|
#ifdef CONFIG_PREEMPT
|
|
static inline void __lock_kernel(void)
|
|
{
|
|
preempt_disable();
|
|
if (unlikely(!do_raw_spin_trylock(&kernel_flag))) {
|
|
/*
|
|
* If preemption was disabled even before this
|
|
* was called, there's nothing we can be polite
|
|
* about - just spin.
|
|
*/
|
|
if (preempt_count() > 1) {
|
|
do_raw_spin_lock(&kernel_flag);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Otherwise, let's wait for the kernel lock
|
|
* with preemption enabled..
|
|
*/
|
|
do {
|
|
preempt_enable();
|
|
while (raw_spin_is_locked(&kernel_flag))
|
|
cpu_relax();
|
|
preempt_disable();
|
|
} while (!do_raw_spin_trylock(&kernel_flag));
|
|
}
|
|
}
|
|
|
|
#else
|
|
|
|
/*
|
|
* Non-preemption case - just get the spinlock
|
|
*/
|
|
static inline void __lock_kernel(void)
|
|
{
|
|
do_raw_spin_lock(&kernel_flag);
|
|
}
|
|
#endif
|
|
|
|
static inline void __unlock_kernel(void)
|
|
{
|
|
/*
|
|
* the BKL is not covered by lockdep, so we open-code the
|
|
* unlocking sequence (and thus avoid the dep-chain ops):
|
|
*/
|
|
do_raw_spin_unlock(&kernel_flag);
|
|
preempt_enable();
|
|
}
|
|
|
|
/*
|
|
* Getting the big kernel lock.
|
|
*
|
|
* This cannot happen asynchronously, so we only need to
|
|
* worry about other CPU's.
|
|
*/
|
|
void __lockfunc _lock_kernel(const char *func, const char *file, int line)
|
|
{
|
|
int depth = current->lock_depth + 1;
|
|
|
|
trace_lock_kernel(func, file, line);
|
|
|
|
if (likely(!depth)) {
|
|
might_sleep();
|
|
__lock_kernel();
|
|
}
|
|
current->lock_depth = depth;
|
|
}
|
|
|
|
void __lockfunc _unlock_kernel(const char *func, const char *file, int line)
|
|
{
|
|
BUG_ON(current->lock_depth < 0);
|
|
if (likely(--current->lock_depth < 0))
|
|
__unlock_kernel();
|
|
|
|
trace_unlock_kernel(func, file, line);
|
|
}
|
|
|
|
EXPORT_SYMBOL(_lock_kernel);
|
|
EXPORT_SYMBOL(_unlock_kernel);
|
|
|