drm/ttm: Fix possible stack overflow by recursive shrinker calls.

[pandora-kernel.git] / drivers / gpu / drm / ttm / ttm_page_alloc.c

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc.c b/drivers/gpu/drm/ttm/ttm_page_alloc.c
index 9e4313e..508c64c 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_page_alloc.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc.c
@@ -398,13 +398,18 @@ static int ttm_pool_get_num_unused_pages(void)
 static int ttm_pool_mm_shrink(struct shrinker *shrink,
                              struct shrink_control *sc)
 {
-       static atomic_t start_pool = ATOMIC_INIT(0);
+       static DEFINE_MUTEX(lock);
+       static unsigned start_pool;
        unsigned i;
-       unsigned pool_offset = atomic_add_return(1, &start_pool);
+       unsigned pool_offset;
        struct ttm_page_pool *pool;
        int shrink_pages = sc->nr_to_scan;
 
-       pool_offset = pool_offset % NUM_POOLS;
+       if (shrink_pages == 0)
+               goto out;
+       if (!mutex_trylock(&lock))
+               return -1;
+       pool_offset = ++start_pool % NUM_POOLS;
        /* select start pool in round robin fashion */
        for (i = 0; i < NUM_POOLS; ++i) {
                unsigned nr_free = shrink_pages;
@@ -413,6 +418,8 @@ static int ttm_pool_mm_shrink(struct shrinker *shrink,
                pool = &_manager->pools[(i + pool_offset)%NUM_POOLS];
                shrink_pages = ttm_page_pool_free(pool, nr_free);
        }
+       mutex_unlock(&lock);
+out:
        /* return estimated number of unused pages in pool */
        return ttm_pool_get_num_unused_pages();
 }