linux-kernel - Re: [PACTH v1] kernel/hung_task.c: Dump all UNINTERUPTIBLE tasks

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Message-ID: <bfb60c11-8717-cb3c-cd3e-42ebc1942eaa@collabora.com>
Date:   Mon, 29 Aug 2016 15:04:51 -0400
From:   Robert Foss <robert.foss@...labora.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     adurbin@...omium.org, penguin-kernel@...ove.SAKURA.ne.jp,
        linux-kernel@...r.kernel.org
Subject: Re: [PACTH v1] kernel/hung_task.c: Dump all UNINTERUPTIBLE tasks



On 2016-08-11 12:35 PM, Robert Foss wrote:
>
>
> On 2016-08-10 06:43 PM, Andrew Morton wrote:
>> On Tue,  2 Aug 2016 11:23:11 -0400 robert.foss@...labora.com wrote:
>>
>>> From: Aaron Durbin <adurbin@...omium.org>
>>>
>>> When the panic path is taken for khungtaskd dump all
>>> tasks with the UNINTERUPTIBLE state. That way, any
>>> inter-dependent tasks that caused one another to hang
>>> will be saved in the crash output.
>>>
>>> ...
>>>
>>> --- a/kernel/hung_task.c
>>> +++ b/kernel/hung_task.c
>>> @@ -122,6 +122,8 @@ static void check_hung_task(struct task_struct
>>> *t, unsigned long timeout)
>>>      touch_nmi_watchdog();
>>>
>>>      if (sysctl_hung_task_panic) {
>>> +        /* Dump all tasks. */
>>> +        show_state_filter(TASK_UNINTERRUPTIBLE);
>>>          trigger_all_cpu_backtrace();
>>>          panic("hung_task: blocked tasks");
>>>      }
>>
>> Well, it's going to produce more gunk for the operator to read through
>> and understand.
>>
>> I'd like to hear a little more about the value of this change: what
>> particular problem prompted it, etc.
>>
>
> It would indeed provide more gunk. What makes it useful is that is on
> enabled by default and enables rapid debugging of devices that are not
> physically accessible or accessible for debugging otherwise.
>
> So the primary usecase would be when a user of a device is seeing some
> issues and submits the logs from the device.
> Without any further action from the user, the problem could potentially
> be solved.

The debug output could be formatted better, would that make this patch 
more appealing?