linux-kernel - Re: [rfcomm_run] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156 __might

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Message-ID: <542D4756.4030100@hurleysoftware.com>
Date:	Thu, 02 Oct 2014 08:38:46 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Fengguang Wu <fengguang.wu@...el.com>
CC:	Jet Chen <jet.chen@...el.com>, Su Tao <tao.su@...el.com>,
	Yuanhan Liu <yuanhan.liu@...el.com>, LKP <lkp@...org>,
	linux-kernel@...r.kernel.org, Marcel Holtmann <marcel@...tmann.org>
Subject: Re: [rfcomm_run] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156
 __might_sleep()

On 10/02/2014 08:31 AM, Peter Zijlstra wrote:
> On Thu, Oct 02, 2014 at 01:09:27PM +0200, Peter Zijlstra wrote:
>> On Tue, Sep 30, 2014 at 04:02:28PM +0800, Fengguang Wu wrote:
>>> Hi Peter,
>>>
>>> We possibly find a rfcomm bug (maintainers CCed) exposed by your debug patch
>>>
>>> [    1.861895] NET: Registered protocol family 5
>>> [    1.862978] Bluetooth: RFCOMM TTY layer initialized
>>> [    1.863099] ------------[ cut here ]------------
>>> [    1.863105] WARNING: CPU: 1 PID: 79 at kernel/sched/core.c:7156 __might_sleep+0x17d/0x1a1()
>>> [    1.863112] do not call blocking ops when !TASK_RUNNING; state=1 set at [<c14dc381>] rfcomm_run+0xdf/0x130e
>>> [    1.863591]  [<c1058b73>] ? kthread_stop+0x53/0x53
>>> [    1.864906]  [<c155a411>] dump_stack+0x48/0x60
>>> [    1.866298]  [<c14dc381>] ? rfcomm_run+0xdf/0x130e
>>
>> Ha yes, rfcomm_run is a complete buggy mess indeed. Lemme go see what I
>> can make of it.
> 
> ---
> Subject: rfcomm: Fix broken wait construct
> 
> rfcomm_run() is a tad broken in that is has a nested wait loop. One
> cannot rely on p->state for the outer wait because the inner wait will
> overwrite it.
> 
> While at it, rename rfcomm_schedule to rfcomm_wake, since that is what
> it actually does.

rfcomm_schedule() as in schedule_work(), which is how it's used.

Regards,
Peter Hurley

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