linux-kernel - Re: [PATCH 1/3] softlockup: add sched_clock_tick() to avoid kernel warning on kgdb resume

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Message-ID: <ce2c83091001312241u89d71fwe4789066684d083a@mail.gmail.com>
Date:	Mon, 1 Feb 2010 14:41:01 +0800
From:	Dongdong Deng <libfetion@...il.com>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	"Deng, Dongdong" <Dongdong.Deng@...driver.com>,
	peterz@...radead.org
Subject: Re: [PATCH 1/3] softlockup: add sched_clock_tick() to avoid kernel 
	warning on kgdb resume

On Mon, Feb 1, 2010 at 2:05 PM, Jason Wessel <jason.wessel@...driver.com> wrote:
> Dongdong Deng wrote:
>> On Fri, Jan 29, 2010 at 10:51 PM, Jason Wessel
>> <jason.wessel@...driver.com> wrote:
>>
>>> echo 3 > /proc/sys/kernel/softlockup_thresh
>>>
>>> And then some kernel code in a thread like:
>>>        local_irq_disable();
>>>        printk("Disable local irq for 11 seconds\n");
>>>        mdelay(11000);
>>>        local_irq_enable();
>>>
>>
>> Hi Jason,
>>
>> Maybe this problem was fixed by
>> commit baf48f6577e581a9adb8fe849dc80e24b21d171d - "softlock: fix false
>> panic which can occur if softlockup_thresh is reduced".
>>
>
>
> That is not the same problem.   The fix you referenced is a corner case
> where you end up with the stack trace at the point in time you reduce
> the threshold.  The only reason I reduce the threshold in the first
> place is just to shorten the amount of time it takes to observe the problem.

Thanks for your nice explanation. :)

Dongdong

> You can just change the numbers for the mdelay and use the default
> softlockup threshold values and still see the problem I reported.
>
> Jason.
>
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