From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752570AbcGFDZy (ORCPT ); Tue, 5 Jul 2016 23:25:54 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:40349 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751271AbcGFDZx (ORCPT ); Tue, 5 Jul 2016 23:25:53 -0400 From: Wei Fang To: CC: , , , , , , Wei Fang , Subject: [PATCH v3] fs/dcache.c: avoid soft-lockup in dput() Date: Wed, 6 Jul 2016 11:32:20 +0800 Message-ID: <1467775940-16711-1-git-send-email-fangwei1@huawei.com> X-Mailer: git-send-email 1.7.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.175.100.166] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A090206.577C7A2F.000D,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: eaf7b281455160a713c186f6a0696b20 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We triggered soft-lockup under stress test which open/access/write/close one file concurrently on more than five different CPUs: WARN: soft lockup - CPU#0 stuck for 11s! [who:30631] ... [] dput+0x100/0x298 [] terminate_walk+0x4c/0x60 [] path_lookupat+0x5cc/0x7a8 [] filename_lookup+0x38/0xf0 [] user_path_at_empty+0x78/0xd0 [] user_path_at+0x1c/0x28 [] SyS_faccessat+0xb4/0x230 ->d_lock trylock may failed many times because of concurrently operations, and dput() may execute a long time. Fix this by replacing cpu_relax() with cond_resched(). dput() used to be sleepable, so make it sleepable again should be safe. Cc: Signed-off-by: Wei Fang --- Changes v1->v2: - add might_sleep() to annotate that dput() can sleep Changes v2->v3: - put cond_resched() in dput() fs/dcache.c | 7 +++++-- 1 files changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index ad4a542..77f6687 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -589,7 +589,6 @@ static struct dentry *dentry_kill(struct dentry *dentry) failed: spin_unlock(&dentry->d_lock); - cpu_relax(); return dentry; /* try again with same dentry */ } @@ -763,6 +762,8 @@ void dput(struct dentry *dentry) return; repeat: + might_sleep(); + rcu_read_lock(); if (likely(fast_dput(dentry))) { rcu_read_unlock(); @@ -796,8 +797,10 @@ repeat: kill_it: dentry = dentry_kill(dentry); - if (dentry) + if (dentry) { + cond_resched(); goto repeat; + } } EXPORT_SYMBOL(dput); -- 1.7.1