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Commit 91b57191 authored by Andrew Morton's avatar Andrew Morton Committed by Linus Torvalds
Browse files

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: default avatarji_ang <ji_ang@163.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fb993fa1

mm/vmpressure.c

+5 −3
Original line number Diff line number Diff line
@@ -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;