linux-kernel - Re: Cpu-Hotplug and Real-Time

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Date:	Tue, 7 Aug 2007 22:36:09 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
Cc:	Gautham R Shenoy <ego@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	linux-kernel@...r.kernel.org, Dipankar Sarma <dipankar@...ibm.com>,
	Paul E McKenney <paulmck@...ibm.com>
Subject: Re: Cpu-Hotplug and Real-Time

On 08/07, Venki Pallipadi wrote:
>
> On Tue, Aug 07, 2007 at 07:13:36PM +0400, Oleg Nesterov wrote:
> > 
> > As for kthread_bind(), I think wait_task_inactive+set_task_cpu is just
> > an optimization, and easy to "fix":
> > 
> > --- kernel/kthread.c	2007-07-28 16:58:17.000000000 +0400
> > +++ /proc/self/fd/0	2007-08-07 18:56:54.248073547 +0400
> > @@ -166,10 +166,7 @@ void kthread_bind(struct task_struct *k,
> >  		WARN_ON(1);
> >  		return;
> >  	}
> > -	/* Must have done schedule() in kthread() before we set_task_cpu */
> > -	wait_task_inactive(k);
> > -	set_task_cpu(k, cpu);
> > -	k->cpus_allowed = cpumask_of_cpu(cpu);
> > +	set_cpus_allowed(current, cpumask_of_cpu(cpu));
> >  }
> >  EXPORT_SYMBOL(kthread_bind);
> > 
> 
> Not sure whether set_cpus_allowed() will work here. Looks like, it needs the
> CPU to be online during the call and in kthread_bind() case CPU may be offline.

Aah, you are right, of course.

Thanks,

Oleg.

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