linux-kernel - Re: stop_machine lockup issue in 3.9.y.

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Message-ID: <51B00719.20406@candelatech.com>
Date:	Wed, 05 Jun 2013 20:50:49 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Tejun Heo <tj@...nel.org>, Rusty Russell <rusty@...tcorp.com.au>,
	Joe Lawrence <joe.lawrence@...atus.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...r.kernel.org,
	"Luis R. Rodriguez" <mcgrof@....qualcomm.com>,
	Jouni Malinen <jouni@....qualcomm.com>,
	Vasanthakumar Thiagarajan <vthiagar@....qualcomm.com>,
	Senthil Balasubramanian <senthilb@....qualcomm.com>,
	linux-wireless@...r.kernel.org, ath9k-devel@...ema.h4ckr.net,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: stop_machine lockup issue in 3.9.y.

On 06/05/2013 08:46 PM, Eric Dumazet wrote:
> On Wed, 2013-06-05 at 20:41 -0700, Ben Greear wrote:
>> On 06/05/2013 08:26 PM, Eric Dumazet wrote:
>>> On Wed, 2013-06-05 at 20:14 -0700, Tejun Heo wrote:
>>>
>>>>
>>>> Ah, so, that's why it's showing up now.  We probably have had the same
>>>> issue all along but it used to be masked by the softirq limiting.  Do
>>>> you care to revive the 10 iterations limit so that it's limited by
>>>> both the count and timing?  We do wanna find out why softirq is
>>>> spinning indefinitely tho.
>>>
>>> Yes, no problem, I can do that.
>>
>> Limiting it to 5000 fixes my problem, so if you wanted it larger than 10, that would
>> be fine by me.
>>
>> I can send a version of my patch easily enough if we can agree on the max number of
>> loops (and if indeed my version of the patch is acceptable).
>
> Well, 10 was the prior limit and seems really fine.
>
> The non update on jiffies seems quite exceptional condition (I hope...)
>
> We use in Google a patch triggering warning is a thread holds the cpu
> without taking care to need_resched() for more than xx ms

Well, I'm sure that patch works nicely until the clock stops moving
forward :)

I'll post a patch with limit of 10 shortly.

Thanks,
Ben



-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

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