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[PATCH 3.2 47/67] mm, vmstat: fix wrong WQ sleep when memory reclaim doesn't make any progress

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3.2.78-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>

commit 564e81a57f9788b1475127012e0fd44e9049e342 upstream.

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.

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")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Jan Stancek <jstancek@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Cristopher Lameter <clameter@sgi.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Arkadiusz Miskiewicz <arekm@maven.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 mm/backing-dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -879,7 +879,7 @@ long wait_iff_congested(struct zone *zon
 		 * here rather than calling cond_resched().
 		 */
 		if (current->flags & PF_WQ_WORKER)
-			schedule_timeout(1);
+			schedule_timeout_uninterruptible(1);
 		else
 			cond_resched();
 

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[PATCH 3.2 47/67] mm, vmstat: fix wrong WQ sleep when memory  reclaim doesn't make any progress Ben Hutchings <ben@decadent.org.uk> - 2016-02-23 23:00 +0100

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