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From: David Howells <dhowells@redhat.com>
To: Andrei Vagin <avagin@gmail.com>
Cc: dhowells@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org,
	Li Zefan <lizefan@huawei.com>
Subject: Re: [PATCH vfs/for-next v2] cgroup: fix top cgroup refcnt leak
Date: Thu, 03 Jan 2019 00:33:13 +0000	[thread overview]
Message-ID: <12708.1546475593@warthog.procyon.org.uk> (raw)
In-Reply-To: <20190102233118.GA19202@gmail.com>

Andrei Vagin <avagin@gmail.com> wrote:

> Here is a reproducer for this problem:
> 
> [root@fc24 ~]# cat fs-vs-cg 
> set -m
> d=$(mktemp -d /tmp/cg.XXXXXX)
> for i in `seq 2`; do 
> 	mkdir $d/a$i
> 	mount -t cgroup -o none,name=xxxxy xxx $d/a$i
> done
> mkdir -p $d/a1/test
> for i in `seq 2`; do 
> 	umount $d/a$i
> done
> d=$(mktemp -d /tmp/cg.XXXXXX)
> for i in `seq 2`; do 
> 	mkdir $d/a$i
> 	mount -t cgroup -o none,name=xxxxy xxx $d/a$i
> done
> rmdir $d/a1/test
> for i in `seq 2`; do 
> 	umount $d/a$i
> done
> 
> You need to execute this script twice and it will stuck on a second
> attmept.

This causes:

	percpu ref (css_release) <= 0 (0) after switching to atomic

without your patch and:

	percpu ref (css_release) <= 0 (-2) after switching to atomic

with your patch, both followed by:

	WARNING: CPU: 0 PID: 0 at lib/percpu-refcount.c:155 percpu_ref_switch_to_atomic_rcu+0x90/0x1a0

on Al's for-next branch.

David

  parent reply	other threads:[~2019-01-03  0:33 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-28 23:59 [PATCH] cgroup: fix top cgroup refcnt leak Andrei Vagin
2018-12-29  0:04 ` [PATCH vfs/for-next v2] " Andrei Vagin
2018-12-30 19:41   ` Andrei Vagin
2019-01-02  2:28   ` Al Viro
2019-01-02 18:14     ` [PATCH vfs/for-next v3] " Andrei Vagin
2019-01-02 19:37     ` [PATCH vfs/for-next v2] " Andrei Vagin
2019-01-02 19:37     ` [PATCH vfs/for-next v4] " Andrei Vagin
2019-01-02 20:02       ` Al Viro
2019-01-02 21:06         ` Andrei Vagin
2019-01-03  0:26         ` David Howells
2019-01-03  0:43           ` Andrei Vagin
2019-01-03  1:00             ` Andrei Vagin
2019-01-03  3:54               ` [PATCH vfs/for-next v6] " Andrei Vagin
2019-01-03  8:32                 ` Al Viro
2019-01-03 17:34                   ` Andrei Vagin
2019-01-03 21:54                   ` David Howells
2019-01-02 22:26 ` [PATCH vfs/for-next v2] " David Howells
2019-01-02 23:06   ` Andrei Vagin
2019-01-02 23:31     ` Andrei Vagin
2019-01-03  0:33     ` David Howells [this message]
2019-01-03 13:41     ` David Howells
2019-01-03 13:42     ` David Howells
2019-01-03 15:27     ` David Howells
2019-01-03 15:44     ` David Howells

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