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mm: Allow to kill tasks doing pcpu_alloc() and waiting for pcpu_balance_workfn()

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In case of memory deficit and low percpu memory pages,
pcpu_balance_workfn() takes pcpu_alloc_mutex for a long
time (as it makes memory allocations itself and waits
for memory reclaim). If tasks doing pcpu_alloc() are
choosen by OOM killer, they can't exit, because they
are waiting for the mutex.

The patch makes pcpu_alloc() to care about killing signal
and use mutex_lock_killable(), when it's allowed by GFP
flags. This guarantees, a task does not miss SIGKILL
from OOM killer.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Kirill Tkhai 2018-03-19 18:32:10 +03:00 committed by Tejun Heo
parent 71546d1004
commit f52ba1fef7
1 changed files with 11 additions and 2 deletions
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13
mm/percpu.c
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@ -1373,8 +1373,17 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
return NULL; return NULL;
} }
if (!is_atomic) if (!is_atomic) {
mutex_lock(&pcpu_alloc_mutex); /*
* pcpu_balance_workfn() allocates memory under this mutex,
* and it may wait for memory reclaim. Allow current task
* to become OOM victim, in case of memory pressure.
*/
if (gfp & __GFP_NOFAIL)
mutex_lock(&pcpu_alloc_mutex);
else if (mutex_lock_killable(&pcpu_alloc_mutex))
return NULL;
}
spin_lock_irqsave(&pcpu_lock, flags); spin_lock_irqsave(&pcpu_lock, flags);