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mm/vmpressure.c: fix race in vmpressure_work_fn() 

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@linux-foundation.org: neaten]
Reported-by: ji_ang <ji_ang@163.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Andrew Morton 2014-12-02 15:59:28 -08:00 committed by Linus Torvalds
parent fb993fa1a2
commit 91b57191cf
1 changed files with 6 additions and 4 deletions
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10
mm/vmpressure.c
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@ -165,6 +165,7 @@ static void vmpressure_work_fn(struct work_struct *work)
unsigned long scanned; unsigned long scanned;
unsigned long reclaimed; unsigned long reclaimed;
spin_lock(&vmpr->sr_lock);
/* /*
* Several contexts might be calling vmpressure(), so it is * Several contexts might be calling vmpressure(), so it is
* possible that the work was rescheduled again before the old * 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 * here. No need for any locks here since we don't care if
* vmpr->reclaimed is in sync. * vmpr->reclaimed is in sync.
*/ */
if (!vmpr->scanned)
return;
spin_lock(&vmpr->sr_lock);
scanned = vmpr->scanned; scanned = vmpr->scanned;
if (!scanned) {
spin_unlock(&vmpr->sr_lock);
return;
}
reclaimed = vmpr->reclaimed; reclaimed = vmpr->reclaimed;
vmpr->scanned = 0; vmpr->scanned = 0;
vmpr->reclaimed = 0; vmpr->reclaimed = 0;