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| author | Wei Fang <fangwei1@huawei.com> | 2016-07-06 11:32:20 +0800 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2016-07-24 16:37:16 -0400 |
| commit | 47be61845c775643f1aa4d2a54343549f943c94c (patch) | |
| tree | 7bc3d07cecb30116a51bdf11dfa0540bfacc4e43 | |
| parent | 285b102d3b745f3c2c110c9c327741d87e64aacc (diff) | |
| download | linux-47be61845c775643f1aa4d2a54343549f943c94c.tar.gz | |
fs/dcache.c: avoid soft-lockup in dput()
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] ... [<ffffffc0003986f8>] dput+0x100/0x298 [<ffffffc00038c2dc>] terminate_walk+0x4c/0x60 [<ffffffc00038f56c>] path_lookupat+0x5cc/0x7a8 [<ffffffc00038f780>] filename_lookup+0x38/0xf0 [<ffffffc000391180>] user_path_at_empty+0x78/0xd0 [<ffffffc0003911f4>] user_path_at+0x1c/0x28 [<ffffffc00037d4fc>] 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: <stable@vger.kernel.org> Signed-off-by: Wei Fang <fangwei1@huawei.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | fs/dcache.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 6d60a764c848..f650a4fc5b7c 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -596,7 +596,6 @@ static struct dentry *dentry_kill(struct dentry *dentry) failed: spin_unlock(&dentry->d_lock); - cpu_relax(); return dentry; /* try again with same dentry */ } @@ -770,6 +769,8 @@ void dput(struct dentry *dentry) return; repeat: + might_sleep(); + rcu_read_lock(); if (likely(fast_dput(dentry))) { rcu_read_unlock(); @@ -803,8 +804,10 @@ repeat: kill_it: dentry = dentry_kill(dentry); - if (dentry) + if (dentry) { + cond_resched(); goto repeat; + } } EXPORT_SYMBOL(dput); |