On Mon, Feb 09, 2015 at 06:06:11PM +0100, Sedat Dilek wrote:

On Mon, Feb 9, 2015 at 5:42 PM, Kirill A. Shutemov [off-list ref] wrote:

quoted

On Sat, Feb 07, 2015 at 08:33:02AM +0100, Sedat Dilek wrote:

quoted

On Sat, Feb 7, 2015 at 6:12 AM, Pat Erley [off-list ref] wrote:

quoted

I'm seeing the message in $subject on my Xen DOM0 on next-20150204 on
x86_64.  I haven't had time to bisect it, but have seen some discussion on
similar topics here recently.  I can trigger this pretty reliably by
watching Netflix.  At some point (minutes to hours) into it, the netflix
video goes black (audio keeps going, so it still thinks it's working) and
the error appears in dmesg.  Refreshing the page gets the video going again,
and it will continue playing for some indeterminate amount of time.

Kirill, I've CC'd you as looking in the logs, you've patched a false
positive trigger of this very recently(patch in kernel I'm running).  Am I
actually hitting a problem, or is this another false positive case? Any
additional details that might help?

Dmesg from system attached.

[ CC some mm folks ]

I have seen this, too.

root# grep "BUG: non-zero nr_pmds on freeing mm:" /var/log/kern.log | wc -l
21

Checking my logs: On next-20150203 and next-20150204.

I am here not in a VM environment and cannot say what causes these messages.

Sorry, my fault.

The patch below should fix that.

From 11bce596e653302e41f819435912f01ca8cbc27e Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <redacted>
Date: Mon, 9 Feb 2015 18:34:56 +0200
Subject: [PATCH] mm: fix race on pmd accounting

Do not account the pmd table to the process if other thread allocated it
under us.

Signed-off-by: Kirill A. Shutemov <redacted>
Reported-by: Sedat Dilek <redacted>

Still building with the fix...

Please feel free to add Pat as a reporter.

     Reported-by: Pat Erley [off-list ref]

Is that fixing...?

commit daa1b0f29cdccae269123e7f8ae0348dbafdc3a7
"mm: account pmd page tables to the process"

If yes, please add a Fixes-tag [2]...

     Fixes: daa1b0f29cdc ("mm: account pmd page tables to the process")

I will re-test with LTP/mmap and report.

The commit is not in Linus tree, so the sha1-id is goinging to change.

-- 
 Kirill A. Shutemov

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