From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753086AbaFJTSH (ORCPT ); Tue, 10 Jun 2014 15:18:07 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:44787 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751851AbaFJTSE convert rfc822-to-8bit (ORCPT ); Tue, 10 Jun 2014 15:18:04 -0400 Date: Tue, 10 Jun 2014 15:17:41 -0400 From: Konrad Rzeszutek Wilk To: Tetsuo Handa 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 Subject: Re: [PATCH 3/5] gpu/drm/ttm: Use mutex_trylock() to avoid deadlock inside shrinker functions. Message-ID: <20140610191741.GA28523@phenom.dumpdata.com> 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> <201405311200.III57894.MLFOOFStQVHJFO@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <201405311200.III57894.MLFOOFStQVHJFO@I-love.SAKURA.ne.jp> User-Agent: Mutt/1.5.23 (2014-03-12) Content-Transfer-Encoding: 8BIT X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 31, 2014 at 12:00:45PM +0900, Tetsuo Handa wrote: > >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; Hmm.. /home/konrad/linux/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c: In function ‘ttm_dma_pool_shrink_scan’: /home/konrad/linux/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c:1015:2: error: invalid use of void expression if (!mutex_lock(&_manager->lock)) This is based on v3.15 with these patches. > 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