Patch "mm, vmstat: fix wrong WQ sleep when memory reclaim doesn't make any progress" has been added to the 4.3-stable tree

This is a note to let you know that I've just added the patch titled

mm, vmstat: fix wrong WQ sleep when memory reclaim doesn't make any progress

to the 4.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-vmstat-fix-wrong-wq-sleep-when-memory-reclaim-doesn-t-make-any-progress.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Tetsuo Handa <[email protected]>
Date: Fri, 5 Feb 2016 15:36:30 -0800
Subject: mm, vmstat: fix wrong WQ sleep when memory reclaim doesn't make any progress

From: Tetsuo Handa <[email protected]>

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.

---
 mm/backing-dev.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -989,7 +989,7 @@ 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();
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.3/mm-oom_kill.c-reverse-the-order-of-setting-tif_memdie-and-sending-sigkill.patch queue-4.3/mm-vmstat-fix-wrong-wq-sleep-when-memory-reclaim-doesn-t-make-any-progress.patch