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Date: Wed, 30 Jul 2008 02:08:20 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: Dave Young <hidave.darkstar@gmail.com>,
	linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org
Subject: Re: [BUG] wireless : cpu stuck for 61s
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	<1217334724.10489.47.camel@johannes.berg>
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On Tue, 29 Jul 2008 14:32:04 +0200 Johannes Berg <johannes@sipsolutions.net> wrote:

> On Tue, 2008-07-29 at 13:57 +0800, Dave Young wrote:
> > While set my wlan0 to ad-hoc mode and then set the essid to something,
> > this bug triggered.
> > 
> > I suspect it's related to debugfs or mutex? But I'm not sure.
> > 
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] BUG: soft lockup - CPU#0 stuck for 61s! [events/0:9]
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] 
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] Pid: 9, comm: events/0 Tainted: G        W (2.6.26-smp #3)
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] EIP: 0060:[<c0450bc3>] EFLAGS: 00000246 CPU: 0
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] EIP is at mutex_lock_nested+0x1b3/0x280
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] EAX: 00000000 EBX: f7bf5284 ECX: f7c7e000 EDX: f7bf52a8
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] ESI: f7bf5288 EDI: 00000246 EBP: f7c7fedc ESP: f7c7fe9c
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493]  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] CR0: 8005003b CR2: b800c5ac CR3: 36e71000 CR4: 000006d0
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493] DR6: ffff0ff0 DR7: 00000400
> > Jul 29 13:01:46 darkstar kernel: [ 8033.736493]  [<c02375a6>] ? debugfs_create_file+0x46/0x210
> 
> It looks like it's getting stuck on
> mutex_lock(&parent->d_inode->i_mutex);
> 
> inside debugfs_create_by_name, but I have no idea why that would happen.
> 

Dave, please try sysrq-W or sysrq-T during that 60 seconds, see if we
can find another task which is holding onto that lock.