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Date:	Mon, 15 Sep 2014 15:09:15 -0700
From:	Kamal Mostafa <>
Cc:	Tetsuo Handa <>,
	Dave Airlie <>,
	Kamal Mostafa <>
Subject: [PATCH 3.13 145/187] drm/ttm: Fix possible division by 0 in ttm_dma_pool_shrink_scan(). -stable review patch.  If anyone has any objections, please let me know.


From: Tetsuo Handa <>

commit 11e504cc705e8ccb06ac93a276e11b5e8fee4d40 upstream.

list_empty(&_manager->pools) being false before taking _manager->lock
does not guarantee that _manager->npools != 0 after taking _manager->lock
because _manager->npools is updated under _manager->lock.

Signed-off-by: Tetsuo Handa <>
Signed-off-by: Dave Airlie <>
Signed-off-by: Kamal Mostafa <>
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index fb8259f..b751fff 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -1015,6 +1015,8 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 		return SHRINK_STOP;
+	if (!_manager->npools)
+		goto out;
 	pool_offset = pool_offset % _manager->npools;
 	list_for_each_entry(p, &_manager->pools, pools) {
 		unsigned nr_free;
@@ -1034,6 +1036,7 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
 			 p->pool->dev_name, p->pool->name, current->pid,
 			 nr_free, shrink_pages);
 	return freed;

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