From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Wei Fang To: CC: , , , , , , Wei Fang , Subject: [PATCH v2] fs/dcache.c: avoid soft-lockup in dput() Date: Wed, 22 Jun 2016 11:01:15 +0800 Message-ID: <1466564475-30417-1-git-send-email-fangwei1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: 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 fs/dcache.c | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/fs/dcache.c b/fs/dcache.c index d5ecc6e..074fc1c 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -578,7 +578,7 @@ static struct dentry *dentry_kill(struct dentry *dentry) failed: spin_unlock(&dentry->d_lock); - cpu_relax(); + cond_resched(); return dentry; /* try again with same dentry */ } @@ -752,6 +752,8 @@ void dput(struct dentry *dentry) return; repeat: + might_sleep(); + rcu_read_lock(); if (likely(fast_dput(dentry))) { rcu_read_unlock(); -- 1.7.1