Re: [PATCH] mm, vmstat: fix wrong WQ sleep when memory reclaim doesn't make any progress
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-01-29 13:40:45
Also in:
linux-mm
On Fri 29-01-16 19:49:12, Tetsuo Handa wrote:
Jan Stancek has reported that system occasionally hanging after
"oom01" testcase from LTP triggers OOM. Guessing from a result that
there is a kworker thread doing memory allocation and the values
between "Node 0 Normal free:" and "Node 0 Normal:" differs when
hanging, vmstat is not up-to-date for some reason.
According to commit 373ccbe59270 ("mm, vmstat: allow WQ concurrency to
discover memory reclaim doesn't make any progress"), it meant to force
the kworker thread to take a short sleep, but it by error used
schedule_timeout(1). We missed that schedule_timeout() in state
TASK_RUNNING doesn't do anything.Dang... You are right of course. I've made the same mistake during oom_reaper development but didn't realize that the same has been used for the WQ thingy. My bad! I am not sure this really fixes the issue mentioned above because I didn't get to look at the report yet but we definitely have to change the task state before calling schedule_timeout so this is obviously correct. I would just argue that the interruptible sleep or TASK_IDLE would be little bit better. But it shouldn't really matter much with such a short timeout I guess.
Fix it by using schedule_timeout_uninterruptible(1) which forces
the kworker thread to take a short sleep in order to make sure
that vmstat is up-to-date.
Fixes: 373ccbe59270 ("mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make any progress")
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Cristopher Lameter <redacted>
Cc: Joonsoo Kim <redacted>
Cc: Arkadiusz Miskiewicz <redacted>
Cc: <redacted>Acked-by: Michal Hocko <mhocko@suse.com> Thanks!
quoted hunk ↗ jump to hunk
--- mm/backing-dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 7340353..cbe6f0b 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c@@ -989,7 +989,7 @@ long wait_iff_congested(struct zone *zone, int sync, long timeout) * here rather than calling cond_resched(). */ if (current->flags & PF_WQ_WORKER) - schedule_timeout(1); + schedule_timeout_uninterruptible(1); else cond_resched();-- 1.8.3.1
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