linux-kernel - Re: [PATCH] cgroups: fix lockdep subclasses overflow

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Message-ID: <49895CAD.1020008@cn.fujitsu.com>
Date:	Wed, 04 Feb 2009 17:15:25 +0800
From:	Li Zefan <lizf@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Paul Menage <menage@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH] cgroups: fix lockdep subclasses overflow

Li Zefan wrote:
> I enabled all cgroup subsystems when compiling kernel, and then:
>  # mount -t cgroup -o net_cls xxx /mnt
>  # mkdir /mnt/0
> 
> This showed up immediately:
>  BUG: MAX_LOCKDEP_SUBCLASSES too low!
>  turning off the locking correctness validator.
> 
> It's caused by the cgroup hierarchy lock:
> 	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
> 		struct cgroup_subsys *ss = subsys[i];
> 		if (ss->root == root)
> 			mutex_lock_nested(&ss->hierarchy_mutex, i);
> 	}
> 
> Now we have 9 cgroup subsystems, and the above 'i' for net_cls is 9, but

sorry, a typo here: the above 'i' for net_cls is 8.

> MAX_LOCKDEP_SUBCLASSES is 8.
> 
> This patch uses different lockdep keys for different subsystems.
> 
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---
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