[patch 09/11] mm, oom_reaper: do not use siglock in try_oom_reaper()

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



From: Michal Hocko <mhocko@xxxxxxxx>
Subject: 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: 3ef22dfff239 ("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@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 mm/oom_kill.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff -puN mm/oom_kill.c~mm-oom_reaper-do-not-use-siglock-in-try_oom_reaper mm/oom_kill.c
--- a/mm/oom_kill.c~mm-oom_reaper-do-not-use-siglock-in-try_oom_reaper
+++ a/mm/oom_kill.c
@@ -625,8 +625,6 @@ void try_oom_reaper(struct task_struct *
 	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 *
 			 * 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 */
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Kernel Newbies FAQ]     [Kernel Archive]     [IETF Annouce]     [DCCP]     [Netdev]     [Networking]     [Security]     [Bugtraq]     [Photo]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux SCSI]

  Powered by Linux