linux-kernel - Re: WARNING: at kernel/rcutree.c:1558 rcu_do_batch+0x386/0x3a0(), during CPU hotplug

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Message-ID: <50532464.5050904@linux.vnet.ibm.com>
Date:	Fri, 14 Sep 2012 18:04:44 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Fengguang Wu <fengguang.wu@...el.com>, paulmck@...ux.vnet.ibm.com,
	jack@...e.cz,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	Tejun Heo <tj@...nel.org>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>
Subject: Re: WARNING: at kernel/rcutree.c:1558 rcu_do_batch+0x386/0x3a0(),
 during CPU hotplug

On 09/14/2012 05:55 PM, Peter Zijlstra wrote:
> On Fri, 2012-09-14 at 17:48 +0530, Srivatsa S. Bhat wrote:
>> #! /bin/bash
> 
> CPUPATH="/sys/devices/system/cpu"
> 
>> NUMBER_OF_CPUS=`ls -d /sys/devices/system/cpu/cpu[0-9]* | wc -l`
> 
> apply the above
> 
>> cd /sys/devices/system/cpu
> 
> skip this, so running the script doesn't change PWD
> 
>> while [ 1 ]
> 
> while :;
> 
>> do
>>         for ((i=1; i < NUMBER_OF_CPUS; i++))
>>         do
>>                 sleep 1;
> 
> Also play with shorter sleeps like: sleep .1, I've found that higher
> hotplug rate triggers some races faster.
> 
>>                 state=`cat cpu$i/online`
>>                 if [ $state -eq 0 ]
>>                 then
>>                         echo 1 > cpu$i/online
>>                 else
>>                         echo 0 > cpu$i/online
> 
> 	echo $((state^1)) > $CPUPATH/cpu$i/online
> 
>>                 fi
>>         done
>> done 
> 
> 

Thanks a lot Peter for your suggestions!

Fengguang, like I had mentioned some time before, somebody had pointed
me to a hotplug test-suite that I believe is being used in LTP.

I have a copy of that suite, which I have attached with this mail.
I have never actually used it seriously before (because I could trigger
bugs with my simple script!), so I don't exactly know what state it is
in ;-)

Regards,
Srivatsa S. Bhat

Download attachment "lhcs_regression-1.6.tgz" of type "application/x-compressed-tar" (17854 bytes)