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Commit cbdcf7f7 authored by Michal Hocko's avatar Michal Hocko Committed by Linus Torvalds
Browse files

mm, oom_reaper: do not use siglock in try_oom_reaper() 

Oleg has noted that siglock usage in try_oom_reaper is both pointless
and dangerous.  signal_group_exit can be checked lockless.  The problem
is that sighand becomes NULL in __exit_signal so we can crash.

Fixes: 3ef22dff ("oom, oom_reaper: try to reap tasks which skip regular OOM killer path")
Link: http://lkml.kernel.org/r/1464679423-30218-1-git-send-email-mhocko@kernel.org


Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
Suggested-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 83b9355b

mm/oom_kill.c

+1 −6
Original line number Diff line number Diff line
@@ -625,8 +625,6 @@ void try_oom_reaper(struct task_struct *tsk) 
	if (atomic_read(&mm->mm_users) > 1) {

		rcu_read_lock();

		for_each_process(p) {

			bool exiting;



			if (!process_shares_mm(p, mm))

				continue;

			if (fatal_signal_pending(p))
@@ -636,10 +634,7 @@ void try_oom_reaper(struct task_struct *tsk) 
			 * If the task is exiting make sure the whole thread group

			 * is exiting and cannot acces mm anymore.

			 */

			spin_lock_irq(&p->sighand->siglock);

			exiting = signal_group_exit(p->signal);

			spin_unlock_irq(&p->sighand->siglock);

			if (exiting)

			if (signal_group_exit(p->signal))

				continue;



			/* Give up */