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Date: Fri, 14 Jan 2011 12:06:52 +0800
From: Li Zefan <lizf@...fujitsu.com>
To: Nick Piggin <npiggin@...il.com>
CC: Valdis.Kletnieks@...edu, containers@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org,
Eric Paris <eparis@...isplace.org>,
Paul Menage <menage@...gle.com>,
Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: linux-next: lockdep whinge in cgroup_rmdir
Nick Piggin wrote:
> On Fri, Jan 14, 2011 at 2:34 AM, <Valdis.Kletnieks@...edu> wrote:
>> Seen booting yesterday's linux-next, was not present in 2.6.37-rc7-mmotm1202.
>>
>> Not sure if it's an selinux or cgroup issue, so I'm throwing it at every
>> address I can find for either. This is easily replicatable and happens at
>> every boot, so I can test patches if needed. Am willing to bisect it down if
>> nobody knows right off the bat what the problem is.
>>
>> The 'W' taint is from the already-reported kernel/workqueue.c worker_enter_idle issue.
>>
>> [ 85.100795] systemd[1]: readahead-replay.service: main process exited, code=exited, status=1
>> [ 85.101530]
>> [ 85.101531] =============================================
>> [ 85.101796] [ INFO: possible recursive locking detected ]
>> [ 85.102002] 2.6.37-next-20110111 #1
>> [ 85.102009] ---------------------------------------------
>> [ 85.102009] systemd/1 is trying to acquire lock:
>> [ 85.102009] (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffff8107ca5c>] cgroup_rmdir+0x339/0x479
>> [ 85.102009]
>> [ 85.102009] but task is already holding lock:
>> [ 85.102009] (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffff8107ca54>] cgroup_rmdir+0x331/0x479
>> [ 85.102009]
>> [ 85.102009] other info that might help us debug this:
>> [ 85.102009] 4 locks held by systemd/1:
>> [ 85.102009] #0: (&sb->s_type->i_mutex_key#14/1){+.+.+.}, at: [<ffffffff810fea4d>] do_rmdir+0x7d/0x121
>> [ 85.102009] #1: (&sb->s_type->i_mutex_key#14){+.+.+.}, at: [<ffffffff810fd4bc>] vfs_rmdir+0x4a/0xbe
>> [ 85.102009] #2: (cgroup_mutex){+.+.+.}, at: [<ffffffff8107cb84>] cgroup_rmdir+0x461/0x479
>> [ 85.102009] #3: (&(&dentry->d_lock)->rlock){+.+...}, at: [<ffffffff8107ca54>] cgroup_rmdir+0x331/0x479
>> [ 85.102009]
>> [ 85.102009] stack backtrace:
>> [ 85.102009] Pid: 1, comm: systemd Tainted: G W 2.6.37-next-20110111 #1
>> [ 85.102009] Call Trace:
>> [ 85.102009] [<ffffffff81069f22>] ? __lock_acquire+0x929/0xd4e
>> [ 85.102009] [<ffffffff8107c6f1>] ? cgroup_clear_directory+0xff/0x131
>> [ 85.102009] [<ffffffff8107c6f1>] ? cgroup_clear_directory+0xff/0x131
>> [ 85.102009] [<ffffffff8107ca5c>] ? cgroup_rmdir+0x339/0x479
>> [ 85.102009] [<ffffffff8106a859>] ? lock_acquire+0x100/0x126
>> [ 85.102009] [<ffffffff8107ca5c>] ? cgroup_rmdir+0x339/0x479
>> [ 85.102009] [<ffffffff815521ef>] ? sub_preempt_count+0x35/0x48
>> [ 85.102009] [<ffffffff8154e401>] ? _raw_spin_lock+0x36/0x45
>> [ 85.102009] [<ffffffff8107ca5c>] ? cgroup_rmdir+0x339/0x479
>> [ 85.102009] [<ffffffff8107ca5c>] ? cgroup_rmdir+0x339/0x479
>> [ 85.102009] [<ffffffff810579cd>] ? autoremove_wake_function+0x0/0x34
>> [ 85.102009] [<ffffffff811e1839>] ? selinux_inode_rmdir+0x15/0x17
>> [ 85.102009] [<ffffffff810fd4eb>] ? vfs_rmdir+0x79/0xbe
>> [ 85.102009] [<ffffffff810feaa0>] ? do_rmdir+0xd0/0x121
>> [ 85.102009] [<ffffffff8100256c>] ? sysret_check+0x27/0x62
>> [ 85.102009] [<ffffffff8106ac79>] ? trace_hardirqs_on_caller+0x117/0x13b
>> [ 85.102009] [<ffffffff8154e201>] ? trace_hardirqs_on_thunk+0x3a/0x3f
>> [ 85.102009] [<ffffffff8110040b>] ? sys_rmdir+0x11/0x13
>> [ 85.102009] [<ffffffff8100253b>] ? system_call_fastpath+0x16/0x1b
>> [ 85.268272] systemd[1]: readahead-collect.service: main process exited, code=exited, status=1
>>
>> Any ideas?
>
> It looks like it is just a missing parent->child lock order annotation, but
> mainline cgroupfs code looks to be OK there. What does
> cgroup_clear_directory() look like in mmotm?
It's not from cgroup_clear_directory()..
This should fix it:
=========================
From: Li Zefan <lizf@...fujitsu.com>
Date: Fri, 14 Jan 2011 11:34:34 +0800
Subject: [PATCH] cgroups: Fix a lockdep warning at cgroup removal
Commit 2fd6b7f5 ("fs: dcache scale subdirs") forgot to annotate a dentry
lock, which caused a lockdep warning.
Reported-by: Valdis Kletnieks <Valdis.Kletnieks@...edu>
Signed-off-by: Li Zefan <lizf@...fujitsu.com>
---
kernel/cgroup.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5c5f4cc..db983e2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -910,7 +910,7 @@ static void cgroup_d_remove_dir(struct dentry *dentry)
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
- spin_lock(&dentry->d_lock);
+ spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
list_del_init(&dentry->d_u.d_child);
spin_unlock(&dentry->d_lock);
spin_unlock(&parent->d_lock);
--
1.7.3.1
--
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