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Oleg Nesterov ee7c82da83 wait_task_stopped: simplify and fix races with SIGCONT/SIGKILL/untrace 
wait_task_stopped() has multiple races with SIGCONT/SIGKILL.  tasklist_lock
does not pin the child in TASK_TRACED/TASK_STOPPED stated, almost all info
reported (including exit_code) may be wrong.

In fact, the code under write_lock_irq(tasklist_lock) is not safe.  The child
may be PTRACE_DETACH'ed at this time by another subthread, in that case it is
possible we are no longer its ->parent.

Change wait_task_stopped() to take ->siglock before inspecting the task.  This
guarantees that the child can't resume and (for example) clear its
->exit_code, so we don't need to use xchg(&p->exit_code) and re-check.  The
only exception is ptrace_stop() which changes ->state and ->exit_code without
->siglock held during abort.  But this can only happen if both the tracer and
the tracee are dying (coredump is in progress), we don't care.

With this patch wait_task_stopped() doesn't move the child to the end of
the ->parent list on success.  This optimization could be restored, but
in that case we have to take write_lock(tasklist) and do some nasty
checks.

Also change the do_wait() since we don't return EAGAIN any longer.

[akpm@linux-foundation.org: fix up after Willy renamed everything]
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:26 -08:00
..
irq genirq: stackdump after the "Trying to free already-free IRQ" message 2008-01-30 13:33:24 +01:00
power PM: documentation cleanups 2008-02-07 01:27:17 -05:00
time time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem 2008-02-06 10:41:03 -08:00
.gitignore gitignore: ignore more generated files 2006-01-03 11:35:26 +01:00
acct.c acct: real_parent ppid 2008-01-07 14:55:37 -08:00
audit.c [AUDIT] ratelimit printk messages audit 2008-02-01 14:25:04 -05:00
audit.h [PATCH] audit: watching subtrees 2007-10-21 02:37:45 -04:00
audit_tree.c [PATCH] audit: watching subtrees 2007-10-21 02:37:45 -04:00
auditfilter.c [AUDIT] make audit=0 really stop audit messages 2008-02-01 14:24:33 -05:00
auditsc.c [AUDIT] create context if auditing was ever enabled 2008-02-01 14:24:45 -05:00
backtracetest.c x86: add a simple backtrace test module 2008-01-30 13:33:08 +01:00
capability.c Add 64-bit capability support to the kernel 2008-02-05 09:44:20 -08:00
cgroup.c Handle pid namespaces in cgroups code 2008-02-07 08:42:22 -08:00
cgroup_debug.c Task Control Groups: simple task cgroup debug info subsystem 2007-10-19 11:53:36 -07:00
compat.c Merge ssh://master.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt 2007-10-18 15:12:41 -07:00
configs.c use simple_read_from_buffer in kernel/ 2007-05-09 12:30:49 -07:00
cpu.c cpu-hotplug: replace per-subsystem mutexes with get_online_cpus() 2008-01-25 21:08:02 +01:00
cpuset.c proc: seqfile convert proc_pid_status to properly handle pid namespaces 2008-02-08 09:22:24 -08:00
delayacct.c Add scaled time to taskstats based process accounting 2007-10-18 14:37:28 -07:00
dma.c whitespace fixes: DMA channel allocator 2007-10-18 14:37:24 -07:00
exec_domain.c whitespace fixes: execution domains 2007-10-18 14:37:26 -07:00
exit.c wait_task_stopped: simplify and fix races with SIGCONT/SIGKILL/untrace 2008-02-08 09:22:26 -08:00
extable.c module: Don't report discarded init pages as kernel text. 2008-01-29 17:13:18 +11:00
fork.c Memory controller: accounting setup 2008-02-07 08:42:18 -08:00
futex.c futex: Add bitset conditional wait/wakeup functionality 2008-02-01 17:45:14 +01:00
futex_compat.c futex: Add bitset conditional wait/wakeup functionality 2008-02-01 17:45:14 +01:00
hrtimer.c timerfd: new timerfd API 2008-02-05 09:44:07 -08:00
itimer.c whitespace fixes: interval timers 2007-10-18 14:37:26 -07:00
kallsyms.c remove support for un-needed _extratext section 2008-02-06 10:41:01 -08:00
Kconfig.hz sched: high-res preemption tick 2008-01-25 21:08:29 +01:00
Kconfig.preempt sched: remove the !PREEMPT_BKL code 2008-01-25 21:08:33 +01:00
kexec.c vmcoreinfo: add "VMCOREINFO_" to all the call for vmcoreinfo_append_str() 2008-02-07 08:42:25 -08:00
kfifo.c is_power_of_2: kernel/kfifo.c 2007-07-16 09:05:50 -07:00
kmod.c Fix unbalanced helper_lock in kernel/kmod.c 2008-01-17 15:38:59 -08:00
kprobes.c kprobes: kretprobe user entry-handler 2008-02-06 10:41:11 -08:00
ksysfs.c Kobject: convert remaining kobject_unregister() to kobject_put() 2008-01-24 20:40:40 -08:00
kthread.c sched: fix, always create kernel threads with normal priority 2008-01-25 21:08:33 +01:00
latencytop.c sched: latencytop support 2008-01-25 21:08:34 +01:00
lockdep.c softlockup: automatically detect hung TASK_UNINTERRUPTIBLE tasks 2008-01-25 21:08:02 +01:00
lockdep_internals.h [PATCH] lockdep: more chains 2006-12-07 08:39:43 -08:00
lockdep_proc.c lockdep: Avoid /proc/lockdep & lock_stat infinite output 2007-10-11 22:11:11 +02:00
Makefile namespaces: cleanup the code managed with PID_NS option 2008-02-08 09:22:23 -08:00
marker.c Linux Kernel Markers: fix marker mutex not taken upon module load 2007-11-14 18:45:40 -08:00
module.c fix "modules: make module_address_lookup() safe" 2008-02-08 09:22:24 -08:00
mutex-debug.c [PATCH] remove many unneeded #includes of sched.h 2007-02-14 08:09:54 -08:00
mutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
mutex.c Add mutex_lock_killable 2007-12-06 17:37:59 -05:00
mutex.h [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
notifier.c kernel/notifier.c should #include <linux/reboot.h> 2008-02-06 10:41:02 -08:00
ns_cgroup.c cgroups: implement namespace tracking subsystem 2007-10-19 11:53:37 -07:00
nsproxy.c namespaces: move the IPC namespace under IPC_NS option 2008-02-08 09:22:23 -08:00
panic.c ACPI: Taint kernel on ACPI table override (format corrected) 2008-02-06 22:07:51 -05:00
params.c kernel/params.c: remove sparse-warning (different signedness) 2008-02-06 10:41:08 -08:00
pid.c namespaces: cleanup the code managed with PID_NS option 2008-02-08 09:22:23 -08:00
pid_namespace.c namespaces: cleanup the code managed with PID_NS option 2008-02-08 09:22:23 -08:00
pm_qos_params.c pm qos infrastructure and interface 2008-02-05 09:44:22 -08:00
posix-cpu-timers.c sched: rt-watchdog: fix .rlim_max = RLIM_INFINITY 2008-01-25 21:08:32 +01:00
posix-timers.c timerfd: new timerfd API 2008-02-05 09:44:07 -08:00
printk.c printk.c: use unsigned ints instead of longs for logbuf index 2008-02-06 10:41:04 -08:00
profile.c debug: clean up kernel/profile.c 2008-01-25 21:08:33 +01:00
ptrace.c ptrace_check_attach: remove unneeded ->signal != NULL check 2008-02-08 09:22:26 -08:00
rcuclassic.c Preempt-RCU: implementation 2008-01-25 21:08:24 +01:00
rcupdate.c Preempt-RCU: fix rcu_barrier for preemptive environment. 2008-01-25 21:08:24 +01:00
rcupreempt.c Preempt-RCU: CPU Hotplug handling 2008-01-25 21:08:25 +01:00
rcupreempt_trace.c Preempt-RCU: implementation 2008-01-25 21:08:24 +01:00
rcutorture.c cpu-hotplug: replace lock_cpu_hotplug() with get_online_cpus() 2008-01-25 21:08:02 +01:00
relay.c relay: nopage 2008-02-06 10:41:07 -08:00
res_counter.c Memory controller improve user interface 2008-02-07 08:42:18 -08:00
resource.c Add IORESOUCE_BUSY flag for System RAM 2007-11-14 18:45:39 -08:00
rtmutex-debug.c Use helpers to obtain task pid in printks 2007-10-19 11:53:43 -07:00
rtmutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex-tester.c Driver core: change sysdev classes to use dynamic kobject names 2008-01-24 20:40:40 -08:00
rtmutex.c Use helpers to obtain task pid in printks 2007-10-19 11:53:43 -07:00
rtmutex.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex_common.h FUTEX: Tidy up the code 2007-07-16 09:05:49 -07:00
rwsem.c sched: mark rwsem functions as __sched for wchan/profiling 2007-12-18 15:21:13 +01:00
sched.c Merge branch 'task_killable' of git://git.kernel.org/pub/scm/linux/kernel/git/willy/misc 2008-02-01 11:45:47 +11:00
sched_debug.c sched: keep total / count stats in addition to the max for 2008-01-25 21:08:35 +01:00
sched_fair.c sched: let +nice tasks have smaller impact 2008-01-31 22:45:22 +01:00
sched_idletask.c sched: high-res preemption tick 2008-01-25 21:08:29 +01:00
sched_rt.c sched: fix goto retry in pick_next_task_rt() 2008-01-25 21:08:34 +01:00
sched_stats.h sched: clean up kernel/sched_stat.h 2007-11-28 15:52:56 +01:00
seccomp.c make seccomp zerocost in schedule 2007-07-16 09:05:50 -07:00
signal.c ptrace_stop: fix the race with ptrace detach+attach 2008-02-08 09:22:26 -08:00
softirq.c time: track accurate idle time with tick_sched.idle_sleeptime 2008-01-30 13:30:04 +01:00
softlockup.c debug: softlockup looping fix 2008-02-02 14:27:45 +11:00
spinlock.c spinlock: lockbreak cleanup 2008-01-30 13:31:20 +01:00
srcu.c make srcu_readers_active() static 2008-02-06 10:41:02 -08:00
stacktrace.c [PATCH] lockdep: stacktrace subsystem, core 2006-07-03 15:27:02 -07:00
stop_machine.c stopmachine: semaphore to mutex 2008-02-06 10:41:08 -08:00
sys.c kernel/sys.c: get rid of expensive divides in groups_sort() 2008-02-06 10:41:09 -08:00
sys_ni.c timerfd: new timerfd API 2008-02-05 09:44:07 -08:00
sysctl.c hugetlb: add locking for overcommit sysctl 2008-02-08 09:22:23 -08:00
sysctl_check.c capabilities: introduce per-process capability bounding set 2008-02-05 09:44:20 -08:00
taskstats.c kernel/taskstats.c: fix bogus nlmsg_free() 2007-11-14 18:45:44 -08:00
test_kprobes.c kprobes: kretprobe user entry-handler 2008-02-06 10:41:11 -08:00
time.c speed up jiffies conversion functions if HZ==USER_HZ 2008-02-06 10:41:10 -08:00
timer.c taskstats scaled time cleanup 2008-02-06 10:41:00 -08:00
tsacct.c Add scaled time to taskstats based process accounting 2007-10-18 14:37:28 -07:00
uid16.c header cleaning: don't include smp_lock.h when not used 2007-05-08 11:15:07 -07:00
user.c namespaces: cleanup the code managed with the USER_NS option 2008-02-08 09:22:23 -08:00
user_namespace.c namespaces: cleanup the code managed with the USER_NS option 2008-02-08 09:22:23 -08:00
utsname.c Fix UTS corruption during clone(CLONE_NEWUTS) 2007-09-19 11:24:17 -07:00
utsname_sysctl.c Isolate the UTS namespace's domainname and hostname back 2007-11-29 09:24:53 -08:00
wait.c wait: Use TASK_NORMAL 2007-12-06 17:34:36 -05:00
workqueue.c cpu-hotplug: replace per-subsystem mutexes with get_online_cpus() 2008-01-25 21:08:02 +01:00