+ oom-add-per-mm-oom-disable-count-protect-oom_disable_count-with-task_lock-in-fork.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     oom: protect oom_disable_count with task_lock in fork
has been added to the -mm tree.  Its filename is
     oom-add-per-mm-oom-disable-count-protect-oom_disable_count-with-task_lock-in-fork.patch

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------------------------------------------------------
Subject: oom: protect oom_disable_count with task_lock in fork
From: David Rientjes <rientjes@google.com>

task_lock(p) protects p->mm->oom_disable_count such that it accurately
represents the number of threads attached to that mm that cannot be killed
by the oom killer.  p->signal->oom_score_adj is never changed without
holding the lock.

This was missed in the fork() path, so we take the lock to ensure checking
its oom_score_adj and decrementing oom_disable_count don't race.

Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/fork.c |    2 ++
 1 file changed, 2 insertions(+)

diff -puN kernel/fork.c~oom-add-per-mm-oom-disable-count-protect-oom_disable_count-with-task_lock-in-fork kernel/fork.c
--- a/kernel/fork.c~oom-add-per-mm-oom-disable-count-protect-oom_disable_count-with-task_lock-in-fork
+++ a/kernel/fork.c
@@ -1304,8 +1304,10 @@ bad_fork_cleanup_namespaces:
 	exit_task_namespaces(p);
 bad_fork_cleanup_mm:
 	if (p->mm) {
+		task_lock(p);
 		if (p->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
 			atomic_dec(&p->mm->oom_disable_count);
+		task_unlock(p);
 		mmput(p->mm);
 	}
 bad_fork_cleanup_signal:
_

Patches currently in -mm which might be from rientjes@google.com are

oom-always-return-a-badness-score-of-non-zero-for-eligible-tasks.patch
linux-next.patch
oom-filter-unkillable-tasks-from-tasklist-dump.patch
oom-add-per-mm-oom-disable-count.patch
oom-add-per-mm-oom-disable-count-protect-oom_disable_count-with-task_lock-in-fork.patch
oom-add-per-mm-oom-disable-count-use-old_mm-for-oom_disable_count-in-exec.patch
oom-avoid-killing-a-task-if-a-thread-sharing-its-mm-cannot-be-killed.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm-fix.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm-fix-fix.patch
oom-rewrite-error-handling-for-oom_adj-and-oom_score_adj-tunables.patch
oom-fix-locking-for-oom_adj-and-oom_score_adj.patch
mm-mempolicy-check-return-code-of-check_range.patch
jbd-remove-dependency-on-__gfp_nofail.patch