linux-kernel - Re: [PATCH resend] Reading POSIX CPU timer from outside the process.

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Date:	Thu, 6 Jan 2011 17:06:29 +0100
From:	torbenh <torbenh@....de>
To:	Dario Faggioli <raistlin@...ux.it>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	john.stultz@...aro.org, roland@...hat.com,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Stanislaw Gruszka <sgruszka@...hat.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Randy Dunlap <rdunlap@...otime.net>
Subject: Re: [PATCH resend] Reading POSIX CPU timer from outside the
 process.

On Tue, Jan 04, 2011 at 12:01:25PM +0100, Dario Faggioli wrote:
> On Thu, 2010-12-30 at 18:45 +0100, torbenh wrote: 
> > > I think we should change glibc if clock_getcpuclockid() doesn't work,
> > > please see below.
> > 
> > http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_getcpuclockid.3.html
> > 
> > this one works.
> > ok... it takes a pthread_t for identifying the thread.
> > but it works.
> > 
> Well, I knew this, I knew it very well, as you can see from the code on
> the git I pointed to (it's part of one of the examples!).
> 
> the thing is that I believe there are situations where it could be
> useful to sample CLOCK_THREAD_CPUTIME_ID from a _different_ process, and
> in that case, you can't access that thread's pthread-id, can you? :-O
> 
> The jack2 code I saw could be one of these "potential user", and AFAICT
> your jack1 might be another one, no?
> Yeah, I know, whether you can/want use this or not also depends on other
> issues, but you are in a _different_ process --and thus you can't use
> pthread_* calls-- aren't you?

i would need to tell the tid to jackd anyways.
i could as well just communicate the clock_id. 

getting the clock_id into the other process is not a problem.
the problem is that i am not allowed to read out the clock.


> 
> I'm now looking at Oleg's solution and into glibc as well... I'll come
> out with something ASAP.
> 
> Regards,
> Dario
> 
> -- 
> <<This happens because I choose it to happen!>> (Raistlin Majere)
> ----------------------------------------------------------------------
> Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)
> 
> http://retis.sssup.it/people/faggioli -- dario.faggioli@...ber.org



-- 
torben Hohn
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