Revision 03049269de433cb5fe2859be9ae4469ceb1163ed authored by Michal Hocko on 25 March 2016, 21:20:33 UTC, committed by Linus Torvalds on 25 March 2016, 23:37:42 UTC
wake_oom_reaper has allowed only 1 oom victim to be queued. The main reason for that was the simplicity as other solutions would require some way of queuing. The current approach is racy and that was deemed sufficient as the oom_reaper is considered a best effort approach to help with oom handling when the OOM victim cannot terminate in a reasonable time. The race could lead to missing an oom victim which can get stuck out_of_memory wake_oom_reaper cmpxchg // OK oom_reaper oom_reap_task __oom_reap_task oom_victim terminates atomic_inc_not_zero // fail out_of_memory wake_oom_reaper cmpxchg // fails task_to_reap = NULL This race requires 2 OOM invocations in a short time period which is not very likely but certainly not impossible. E.g. the original victim might have not released a lot of memory for some reason. The situation would improve considerably if wake_oom_reaper used a more robust queuing. This is what this patch implements. This means adding oom_reaper_list list_head into task_struct (eat a hole before embeded thread_struct for that purpose) and a oom_reaper_lock spinlock for queuing synchronization. wake_oom_reaper will then add the task on the queue and oom_reaper will dequeue it. Signed-off-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: Andrea Argangeli <andrea@kernel.org> Cc: David Rientjes <rientjes@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent bc448e8
clz_ctz.c
/*
* lib/clz_ctz.c
*
* Copyright (C) 2013 Chanho Min <chanho.min@lge.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
* The functions in this file aren't called directly, but are required by
* GCC builtins such as __builtin_ctz, and therefore they can't be removed
* despite appearing unreferenced in kernel source.
*
* __c[lt]z[sd]i2 can be overridden by linking arch-specific versions.
*/
#include <linux/export.h>
#include <linux/kernel.h>
int __weak __ctzsi2(int val);
int __weak __ctzsi2(int val)
{
return __ffs(val);
}
EXPORT_SYMBOL(__ctzsi2);
int __weak __clzsi2(int val);
int __weak __clzsi2(int val)
{
return 32 - fls(val);
}
EXPORT_SYMBOL(__clzsi2);
int __weak __clzdi2(long val);
int __weak __ctzdi2(long val);
#if BITS_PER_LONG == 32
int __weak __clzdi2(long val)
{
return 32 - fls((int)val);
}
EXPORT_SYMBOL(__clzdi2);
int __weak __ctzdi2(long val)
{
return __ffs((u32)val);
}
EXPORT_SYMBOL(__ctzdi2);
#elif BITS_PER_LONG == 64
int __weak __clzdi2(long val)
{
return 64 - fls64((u64)val);
}
EXPORT_SYMBOL(__clzdi2);
int __weak __ctzdi2(long val)
{
return __ffs64((u64)val);
}
EXPORT_SYMBOL(__ctzdi2);
#else
#error BITS_PER_LONG not 32 or 64
#endif
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