linux-kernel - Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send

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Date:	Wed, 05 Jun 2013 16:12:45 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Jiri Kosina <jkosina@...e.cz>
CC:	Borislav Petkov <bp@...en8.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Tony Luck <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule,
 round 2

On 06/05/2013 04:08 PM, Jiri Kosina wrote:
> On Wed, 5 Jun 2013, Michael Wang wrote:
> 
>>> Just to not let this thread sleep -- I am seeing this as well, even with 
>>> current Linus' tree (git HEAD == aa4f608).
>>
>> Have you tried this:
>>
>> diff --git a/drivers/cpufreq/cpufreq_governor.c
>> b/drivers/cpufreq/cpufreq_governor.c
>> index 443442d..449be88 100644
>> --- a/drivers/cpufreq/cpufreq_governor.c
>> +++ b/drivers/cpufreq/cpufreq_governor.c
>> @@ -26,6 +26,7 @@
>>  #include <linux/tick.h>
>>  #include <linux/types.h>
>>  #include <linux/workqueue.h>
>> +#include <linux/cpu.h>
>>
>>  #include "cpufreq_governor.h"
>>
>> @@ -180,8 +181,10 @@ void gov_queue_work(struct dbs_data *dbs_data,
>> struct cpufreq_policy *policy,
>>         if (!all_cpus) {
>>                 __gov_queue_work(smp_processor_id(), dbs_data, delay);
>>         } else {
>> +               get_online_cpus();
>>                 for_each_cpu(i, policy->cpus)
>>                         __gov_queue_work(i, dbs_data, delay);
>> +               put_online_cpus();
>>         }
>>  }
>>  EXPORT_SYMBOL_GPL(gov_queue_work);
>>
>> Does it works?
> 
> Yes, the warning is gone with this patch.

Nice, so I think we proved that 'policy->cpus' is well maintained.

> 
> 	Tested-by: Jiri Kosina <jkosina@...e.cz>

Thanks for your testing :)

Regards,
Michael Wang

> 
> Thanks,
> 

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