linux-kernel - Re: [PATCH 04/45] CPU hotplug: Add infrastructure to check lacking hotplug synchronization

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Message-ID: <51C9E647.90306@linux.vnet.ibm.com>
Date:	Wed, 26 Jun 2013 00:19:43 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	tglx@...utronix.de, peterz@...radead.org, tj@...nel.org,
	oleg@...hat.com, paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
	mingo@...nel.org, akpm@...ux-foundation.org, namhyung@...nel.org,
	walken@...gle.com, vincent.guittot@...aro.org,
	laijs@...fujitsu.com, wangyun@...ux.vnet.ibm.com,
	xiaoguangrong@...ux.vnet.ibm.com, sbw@....edu, fweisbec@...il.com,
	zhong@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com,
	linux-pm@...r.kernel.org, linux-arch@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Alex Shi <alex.shi@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH 04/45] CPU hotplug: Add infrastructure to check lacking
 hotplug synchronization

On 06/25/2013 04:56 AM, Steven Rostedt wrote:
> On Sun, 2013-06-23 at 19:08 +0530, Srivatsa S. Bhat wrote:
> 
> 
> Just to make the code a little cleaner, can you add:
> 
>> diff --git a/kernel/cpu.c b/kernel/cpu.c
>> index 860f51a..e90d9d7 100644
>> --- a/kernel/cpu.c
>> +++ b/kernel/cpu.c
>> @@ -63,6 +63,72 @@ static struct {
>>  	.refcount = 0,
>>  };
>>  
>> +#ifdef CONFIG_DEBUG_HOTPLUG_CPU
>> +
[..]
> 
> static inline void atomic_reader_refcnt_inc(void)
> {
> 	this_cpu_inc(atomic_reader_refcnt);
> }
> static inline void atomic_reader_refcnt_dec(void)
> {
> 	this_cpu_dec(atomic_reader_refcnt);
> }
> 
> #else
> static inline void atomic_reader_refcnt_inc(void)
> {
> }
> static inline void atomic_reader_refcnt_dec(void)
> {
> }
> #endif
> 
>> +#endif
>> +
>>  void get_online_cpus(void)
>>  {
>>  	might_sleep();
>> @@ -189,13 +255,22 @@ unsigned int get_online_cpus_atomic(void)
>>  	 * from going offline.
>>  	 */
>>  	preempt_disable();
>> +
>> +#ifdef CONFIG_DEBUG_HOTPLUG_CPU
>> +	this_cpu_inc(atomic_reader_refcnt);
>> +#endif
> 
> Replace the #ifdef with just:
> 
> 	atomic_reader_refcnt_inc();
> 
>>  	return smp_processor_id();
>>  }
>>  EXPORT_SYMBOL_GPL(get_online_cpus_atomic);
>>  
>>  void put_online_cpus_atomic(void)
>>  {
>> +
>> +#ifdef CONFIG_DEBUG_HOTPLUG_CPU
>> +	this_cpu_dec(atomic_reader_refcnt);
>> +#endif
> 
> And
> 
> 	atomic_reader_refcnt_dec();
> 

This makes the code look much better. Thank you!
I'll make that change in my v2.

Regards,
Srivatsa S. Bhat

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