3.2.63-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
commit 71336e011d1d2312bcbcaa8fcec7365024f3a95d upstream.
While ttm_dma_pool_shrink_scan() tries to take mutex before doing GFP_KERNEL
allocation, ttm_pool_shrink_scan() does not do it. This can result in stack
overflow if kmalloc() in ttm_page_pool_free() triggered recursion due to
memory pressure.
shrink_slab()
=> ttm_pool_shrink_scan()
=> ttm_page_pool_free()
=> kmalloc(GFP_KERNEL)
=> shrink_slab()
=> ttm_pool_shrink_scan()
=> ttm_page_pool_free()
=> kmalloc(GFP_KERNEL)
Change ttm_pool_shrink_scan() to do like ttm_dma_pool_shrink_scan() does.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx>
[bwh: Backported to 3.2:
- Adjust context
- Change return value in the contended case to follow the old shrinker
API]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- 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
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 shr
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();
}
--
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