linux-kernel - Re: 2.6.21-rc7-mm1 + sysfs-oops-workaround.patch -- INFO: possible recursive locking detected

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Date:	Wed, 25 Apr 2007 14:18:47 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Miles Lane <miles.lane@...il.com>
CC:	Andrew Morton <akpm@...l.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.21-rc7-mm1 + sysfs-oops-workaround.patch -- INFO: possible
 recursive locking detected

Miles Lane wrote:
> [   59.677312] NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state
> recovery directory
> [   59.688633] NFSD: starting 90-second grace period
> [   60.221454]
> [   60.221456] =============================================
> [   60.221461] [ INFO: possible recursive locking detected ]
> [   60.221464] 2.6.21-rc7-mm1 #53
> [   60.221466] ---------------------------------------------
> [   60.221469] S20powernowd/3584 is trying to acquire lock:
> [   60.221472]  (&sd->s_active){----}, at: [<c01a2436>]
> sysfs_hash_and_remove+0x91/0x10e
> [   60.221486]
> [   60.221487] but task is already holding lock:
> [   60.221489]  (&sd->s_active){----}, at: [<c01a2a20>]
> sysfs_write_file+0xb9/0x14a
> [   60.221496]
> [   60.221497] other info that might help us debug this:
> [   60.221499] 4 locks held by S20powernowd/3584:
> [   60.221501]  #0:  (&sd->s_active){----}, at: [<c01a2a20>]
> sysfs_write_file+0xb9/0x14a
> [   60.221508]  #1:  (&sd->s_active){----}, at: [<c01a2a32>]
> sysfs_write_file+0xcb/0x14a
> [   60.221515]  #2:  (&per_cpu(cpu_policy_rwsem, cpu)){--..}, at:
> [<c024081b>] lock_policy_rwsem_write+0x20/0x37
> [   60.221524]  #3:  (userspace_mutex){--..}, at: [<c0299dfe>]
> mutex_lock+0x1f/0x23

Thanks for reporting.  We need to separate s_active users into two
classes - one for r/w the other for deleting for nodes which delete
other nodes when written to.  Will post a patch soon.

-- 
tejun
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