mm: oom_kill: generalize OOM progress waitqueue

It turns out that the mechanism to wait for exiting OOM victims is less
generic than it looks: it won't issue wakeups unless the OOM killer is
disabled.

The reason this check was added was the thought that, since only the OOM
disabling code would wait on this queue, wakeup operations could be
saved when that specific consumer is known to be absent.

However, this is quite the handgrenade.  Later attempts to reuse the
waitqueue for other purposes will lead to completely unexpected bugs and
the failure mode will appear seemingly illogical.  Generally, providers
shouldn't make unnecessary assumptions about consumers.

This could have been replaced with waitqueue_active(), but it only saves
a few instructions in one of the coldest paths in the kernel.  Simply
remove it.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Johannes Weiner 2015-06-24 16:57:13 -07:00 committed by Linus Torvalds
parent 464027785f
commit c38f1025f2
1 changed files with 1 additions and 5 deletions

View File

@ -438,11 +438,7 @@ void exit_oom_victim(void)
clear_thread_flag(TIF_MEMDIE);
down_read(&oom_sem);
/*
* There is no need to signal the lasst oom_victim if there
* is nobody who cares.
*/
if (!atomic_dec_return(&oom_victims) && oom_killer_disabled)
if (!atomic_dec_return(&oom_victims))
wake_up_all(&oom_victims_wait);
up_read(&oom_sem);
}