From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tetsuo Handa Subject: [PATCH 3/5] gpu/drm/ttm: Use mutex_trylock() to avoid deadlock inside shrinker functions. Date: Sat, 31 May 2014 12:00:45 +0900 Message-ID: <201405311200.III57894.MLFOOFStQVHJFO@I-love.SAKURA.ne.jp> References: <201405290647.DHI69200.HSFVFMFOJOLOQt@I-love.SAKURA.ne.jp> <201405292334.EAG00503.FLOOJFStHVQMFO@I-love.SAKURA.ne.jp> <20140530160824.GD3621@localhost.localdomain> <201405311158.DGE64002.QLOOHJSFFMVFOt@I-love.SAKURA.ne.jp> <201405311159.CHG64048.SOFLQHVtFOMFJO@I-love.SAKURA.ne.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <201405311159.CHG64048.SOFLQHVtFOMFJO@I-love.SAKURA.ne.jp> Sender: linux-kernel-owner@vger.kernel.org To: konrad.wilk@oracle.com Cc: dchinner@redhat.com, airlied@linux.ie, glommer@openvz.org, mgorman@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org List-Id: linux-mm.kvack.org >>From 4e8d1a83629c5966bfd401c5f2187355624194f2 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Sat, 31 May 2014 09:59:44 +0900 Subject: [PATCH 3/5] gpu/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+] --- drivers/gpu/drm/ttm/ttm_page_alloc_dma.c | 6 ++++-- 1 files 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 d8e59f7..620da39 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_lock(&_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); -- 1.7.1