From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Sun, 3 Aug 2014 11:00:40 +0000 (+0900)
Subject: drm/ttm: Choose a pool to shrink correctly in ttm_dma_pool_shrink_scan().
X-Git-Tag: firefly_0821_release~3679^2~1538
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a0fe26d09596ccb84f68603f02c4c78a6394e9f9;p=firefly-linux-kernel-4.4.55.git

drm/ttm: Choose a pool to shrink correctly in ttm_dma_pool_shrink_scan().

commit 46c2df68f03a236b30808bba361f10900c88d95e upstream.

We can use "unsigned int" instead of "atomic_t" by updating start_pool
variable under _manager->lock. This patch will make it possible to avoid
skipping when choosing a pool to shrink in round-robin style, after next
patch changes mutex_lock(_manager->lock) to !mutex_trylock(_manager->lork).

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index e9f65ad2a0eb..de1a753b1d56 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -1006,9 +1006,9 @@ EXPORT_SYMBOL_GPL(ttm_dma_unpopulate);
 static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
 				  struct shrink_control *sc)
 {
-	static atomic_t start_pool = ATOMIC_INIT(0);
+	static unsigned start_pool;
 	unsigned idx = 0;
-	unsigned pool_offset = atomic_add_return(1, &start_pool);
+	unsigned pool_offset;
 	unsigned shrink_pages = sc->nr_to_scan;
 	struct device_pools *p;
 
@@ -1018,7 +1018,7 @@ static int ttm_dma_pool_mm_shrink(struct shrinker *shrink,
 	mutex_lock(&_manager->lock);
 	if (!_manager->npools)
 		goto out;
-	pool_offset = pool_offset % _manager->npools;
+	pool_offset = ++start_pool % _manager->npools;
 	list_for_each_entry(p, &_manager->pools, pools) {
 		unsigned nr_free;