Commit f52ba1fe authored Mar 19, 2018 by Kirill Tkhai Committed by Tejun Heo Mar 19, 2018

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



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>

parent 71546d10

mm/percpu.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -1373,8 +1373,17 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved,
		return NULL;
		}

		if (!is_atomic)
		if (!is_atomic) {
		/*
		* 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);

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