linux-kernel - Re: rcu_preempt detected stalls.

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Message-ID: <54494F2F.6020005@oracle.com>
Date:	Thu, 23 Oct 2014 14:55:43 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, htejun@...il.com
Subject: Re: rcu_preempt detected stalls.

On 10/23/2014 02:39 PM, Paul E. McKenney wrote:
> On Tue, Oct 14, 2014 at 10:35:10PM -0400, Sasha Levin wrote:
>> On 10/13/2014 01:35 PM, Dave Jones wrote:
>>> oday in "rcu stall while fuzzing" news:
>>>
>>> INFO: rcu_preempt detected stalls on CPUs/tasks:
>>> 	Tasks blocked on level-0 rcu_node (CPUs 0-3): P766 P646
>>> 	Tasks blocked on level-0 rcu_node (CPUs 0-3): P766 P646
>>> 	(detected by 0, t=6502 jiffies, g=75434, c=75433, q=0)
>>
>> I've complained about RCU stalls couple days ago (in a different context)
>> on -next. I guess whatever causing them made it into Linus's tree?
>>
>> https://lkml.org/lkml/2014/10/11/64
> 
> And on that one, I must confess that I don't see where the RCU read-side
> critical section might be.
> 
> Hmmm...  Maybe someone forgot to put an rcu_read_unlock() somewhere.
> Can you reproduce this with CONFIG_PROVE_RCU=y?

Paul, if that was directed to me - Yes, I see stalls with CONFIG_PROVE_RCU
set and nothing else is showing up before/after that.


Thanks,
Sasha

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