linux-kernel - Re: [RFC][PATCH 2/4] Revert Changes to kernel/workqueue.c

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Message-ID: <20060824110248.GF2395@in.ibm.com>
Date:	Thu, 24 Aug 2006 16:32:49 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Gautham R Shenoy <ego@...ibm.com>, rusty@...tcorp.com.au,
	torvalds@...l.org, akpm@...l.org, linux-kernel@...r.kernel.org,
	arjan@...el.linux.com, mingo@...e.hu, davej@...hat.com,
	vatsa@...ibm.com, dipankar@...ibm.com, ashok.raj@...el.com
Subject: Re: [RFC][PATCH 2/4] Revert Changes to kernel/workqueue.c

On Thu, Aug 24, 2006 at 12:51:00PM +0200, Heiko Carstens wrote:
> > @@ -510,13 +515,11 @@ int schedule_on_each_cpu(void (*func)(vo
> >  	if (!works)
> >  		return -ENOMEM;
> >  
> > -	mutex_lock(&workqueue_mutex);
> >  	for_each_online_cpu(cpu) {
> >  		INIT_WORK(per_cpu_ptr(works, cpu), func, info);
> >  		__queue_work(per_cpu_ptr(keventd_wq->cpu_wq, cpu),
> >  				per_cpu_ptr(works, cpu));
> >  	}
> > -	mutex_unlock(&workqueue_mutex);
> >  	flush_workqueue(keventd_wq);
> >  	free_percpu(works);
> >  	return 0;
> 
> Removing this lock without adding a lock/unlock_cpu_hotplug seems wrong,
> since this function is walking the cpu_online_map.
I had thought of it. But later decided to retain the same code as 2.6.18-rc4,
where there was no lock_cpu_hotplug surrounding for_each_online_cpu.

Furthermore, it did not create any problems with the test run.
So I thought *may-be* we don't need it. 
But looks like I need to investigate further.
Thanks for pointing it out.

Regards
ego.
-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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