linux-kernel - Re: [PATCH 02/10] posix-timers: Remove dead process posix cpu timers caching

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Date:	Thu, 5 Dec 2013 01:32:03 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	tglx@...utronix.de, mingo@...nel.org, linux-kernel@...r.kernel.org,
	peterz@...radead.org, oleg@...hat.com, akpm@...ux-foundation.org
Subject: Re: [PATCH 02/10] posix-timers: Remove dead process posix cpu timers
 caching

On Wed, Dec 04, 2013 at 01:50:34PM -0500, KOSAKI Motohiro wrote:
> > @@ -1090,13 +1063,8 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
> >  			timer->it.cpu.expires = 0;
> >  			goto out_unlock;
> >  		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
> > -			/*
> > -			 * We've noticed that the thread is dead, but
> > -			 * not yet reaped.  Take this opportunity to
> > -			 * drop our task ref.
> > -			 */
> > +			/* Optimizations: if the process is dying, no need to rearm */
> >  			cpu_timer_sample_group(timer->it_clock, p, &now);
> 
> Why do we still need to call cpu_timer_sample_group? You removed to below line which uses
> "now".

Good point, it looks safe to remove it now.

Thanks.
 
> > -			clear_dead_task(timer, now);
> >  			goto out_unlock;
> >  		}
> >  		spin_lock(&p->sighand->siglock);
> > 
> 
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