From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 22e71691fd54c637800d10816bbeba9cf132d218 upstream. I can observe that RHEL7 environment stalls with 100% CPU usage when a certain type of memory pressure is given. While the shrinker functions are called by shrink_slab() before the OOM killer is triggered, the stall lasts for many minutes. One of reasons of this stall is that ttm_dma_pool_shrink_count()/ttm_dma_pool_shrink_scan() are called and are blocked at mutex_lock(&_manager->lock). GFP_KERNEL allocation with _manager->lock held causes someone (including kswapd) to deadlock when these functions are called due to memory pressure. This patch changes "mutex_lock();" to "if (!mutex_trylock()) return ...;" in order to avoid deadlock. Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Dave Airlie <airlied@xxxxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c index 5d49274afd0e..629e344dad1e 100644 --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c @@ -1013,7 +1013,8 @@ ttm_dma_pool_shrink_scan(struct shrinker *shrink, struct shrink_control *sc) if (list_empty(&_manager->pools)) return SHRINK_STOP; - mutex_lock(&_manager->lock); + if (!mutex_trylock(&_manager->lock)) + return SHRINK_STOP; if (!_manager->npools) goto out; pool_offset = ++start_pool % _manager->npools; @@ -1046,7 +1047,8 @@ ttm_dma_pool_shrink_count(struct shrinker *shrink, struct shrink_control *sc) struct device_pools *p; unsigned long count = 0; - mutex_lock(&_manager->lock); + if (!mutex_trylock(&_manager->lock)) + return 0; list_for_each_entry(p, &_manager->pools, pools) count += p->pool->npages_free; mutex_unlock(&_manager->lock); -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html