From: Kirill Tkhai Date: Mon, 19 Mar 2018 15:32:10 +0000 (+0300) Subject: mm: Allow to kill tasks doing pcpu_alloc() and waiting for pcpu_balance_workfn() X-Git-Tag: v4.19~1415^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f52ba1fef7b92e74d58efef8eae7b6f48c6d218d;p=platform%2Fkernel%2Flinux-rpi.git 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 Signed-off-by: Tejun Heo --- diff --git a/mm/percpu.c b/mm/percpu.c index 15a398c..9297098 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1373,8 +1373,17 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, return NULL; } - if (!is_atomic) - mutex_lock(&pcpu_alloc_mutex); + 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);