Commit c38f1025 authored by Johannes Weiner's avatar Johannes Weiner Committed by Linus Torvalds

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: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Acked-by: default avatarDavid 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 46402778
...@@ -438,11 +438,7 @@ void exit_oom_victim(void) ...@@ -438,11 +438,7 @@ void exit_oom_victim(void)
clear_thread_flag(TIF_MEMDIE); clear_thread_flag(TIF_MEMDIE);
down_read(&oom_sem); down_read(&oom_sem);
/* if (!atomic_dec_return(&oom_victims))
* 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)
wake_up_all(&oom_victims_wait); wake_up_all(&oom_victims_wait);
up_read(&oom_sem); up_read(&oom_sem);
} }
......
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