[3.16.y-ckt stable] Patch "mm/vmpressure.c: fix race in vmpressure_work_fn()" has been added to staging queue
Luis Henriques
luis.henriques at canonical.com
Wed Dec 10 17:26:52 UTC 2014
This is a note to let you know that I have just added a patch titled
mm/vmpressure.c: fix race in vmpressure_work_fn()
to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue
This patch is scheduled to be released in version 3.16.7-ckt3.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Luis
------
>From a4d42590d3602d8270f2691b9d827f4397c74501 Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm at linux-foundation.org>
Date: Tue, 2 Dec 2014 15:59:28 -0800
Subject: mm/vmpressure.c: fix race in vmpressure_work_fn()
commit 91b57191cfd152c02ded0745250167d0263084f8 upstream.
In some android devices, there will be a "divide by zero" exception.
vmpr->scanned could be zero before spin_lock(&vmpr->sr_lock).
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=88051
[akpm at linux-foundation.org: neaten]
Reported-by: ji_ang <ji_ang at 163.com>
Cc: Anton Vorontsov <anton.vorontsov at linaro.org>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
mm/vmpressure.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index d4042e75f7c7..c5afd573d7da 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -165,6 +165,7 @@ static void vmpressure_work_fn(struct work_struct *work)
unsigned long scanned;
unsigned long reclaimed;
+ spin_lock(&vmpr->sr_lock);
/*
* Several contexts might be calling vmpressure(), so it is
* possible that the work was rescheduled again before the old
@@ -173,11 +174,12 @@ static void vmpressure_work_fn(struct work_struct *work)
* here. No need for any locks here since we don't care if
* vmpr->reclaimed is in sync.
*/
- if (!vmpr->scanned)
+ scanned = vmpr->scanned;
+ if (!scanned) {
+ spin_unlock(&vmpr->sr_lock);
return;
+ }
- spin_lock(&vmpr->sr_lock);
- scanned = vmpr->scanned;
reclaimed = vmpr->reclaimed;
vmpr->scanned = 0;
vmpr->reclaimed = 0;
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