From: Tetsuo Handa Date: Sun, 3 Aug 2014 11:01:10 +0000 (+0900) Subject: drm/ttm: Use mutex_trylock() to avoid deadlock inside shrinker functions. X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=22e71691fd54c637800d10816bbeba9cf132d218;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git drm/ttm: Use mutex_trylock() to avoid deadlock inside shrinker functions. 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 Cc: stable [3.3+] Signed-off-by: Dave Airlie --- diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c index d8e59f7b58b2..524cc1a2c1fa 100644 --- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c +++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c @@ -1014,7 +1014,8 @@ 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; @@ -1047,7 +1048,8 @@ 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);