oom: remove oom_disable_count
authorDavid Rientjes <rientjes@google.com>
Tue, 1 Nov 2011 00:07:15 +0000 (17:07 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 1 Nov 2011 00:30:45 +0000 (17:30 -0700)
commitc9f01245b6a7d77d17deaa71af10f6aca14fa24e
tree13ffde591a5bcefba39cb6393f09b27f1ebc1a30
parent7b0d44fa49b1dcfdcf4897f12ddd12ddeab1a9d7
oom: remove oom_disable_count

This removes mm->oom_disable_count entirely since it's unnecessary and
currently buggy.  The counter was intended to be per-process but it's
currently decremented in the exit path for each thread that exits, causing
it to underflow.

The count was originally intended to prevent oom killing threads that
share memory with threads that cannot be killed since it doesn't lead to
future memory freeing.  The counter could be fixed to represent all
threads sharing the same mm, but it's better to remove the count since:

 - it is possible that the OOM_DISABLE thread sharing memory with the
   victim is waiting on that thread to exit and will actually cause
   future memory freeing, and

 - there is no guarantee that a thread is disabled from oom killing just
   because another thread sharing its mm is oom disabled.

Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Cc: Ying Han <yinghan@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
fs/exec.c
fs/proc/base.c
include/linux/mm_types.h
kernel/exit.c
kernel/fork.c
mm/oom_kill.c