linux-kernel - Re: [PATCH] posix_cpu_timers: fix timer never expires when executes clock

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Message-ID: <20130801131117.GK6721@zhudong.nay.redhat.com>
Date:	Thu, 1 Aug 2013 21:11:17 +0800
From:	Dong Zhu <bluezhudong@...il.com>
To:	Stanislaw Gruszka <sgruszka@...hat.com>
Cc:	John Stultz <john.stultz@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oleg Nesterov <oleg@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] posix_cpu_timers: fix timer never expires when
 executes clock_nanosleep

Hi Stanislaw,

Thansk for your info.

On Thu, Aug 01, 2013 at 01:30:50PM +0200, Stanislaw Gruszka wrote:
> Hi Dong Zhu
> 
> On Thu, Aug 01, 2013 at 06:10:19PM +0800, Dong Zhu wrote:
> > diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> > index c7f31aa..cc03290 100644
> > --- a/kernel/posix-cpu-timers.c
> > +++ b/kernel/posix-cpu-timers.c
> > @@ -1413,9 +1413,9 @@ static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
> >  	/*
> >  	 * Diagnose required errors first.
> >  	 */
> > -	if (CPUCLOCK_PERTHREAD(which_clock) &&
> > -	    (CPUCLOCK_PID(which_clock) == 0 ||
> > -	     CPUCLOCK_PID(which_clock) == current->pid))
> > +	if (CPUCLOCK_PID(which_clock) == current->pid ||
> > +	    (CPUCLOCK_PERTHREAD(which_clock) &&
> > +	     CPUCLOCK_PID(which_clock) == 0))
> >  		return -EINVAL;
> 
> Nope, this is wrong. We have to allow own pid process clock, because it
> can be used correctly on multi-threaded processes. Own tid thread clock

Yes, you are right, I really neglected this point.

> has no sense and we correctly return -EINVAL in such case.

> 
> We could possibly add check for own pid together with check if process 
> consist of one thread, but that is too complicated IMHO especially
> taking into account that threads on the process can be destroyed and
> created dynamically.
> 

Agree, really so complicated.

-- 
Best Regards,
Dong Zhu
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