linux-kernel - Re: setitimer vs. threads: SIGALRM returned to which thread? (process master or individual child)

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Date:	Sun, 11 Apr 2010 14:52:12 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Frantisek Rysanek <Frantisek.Rysanek@...t.cz>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: setitimer vs. threads: SIGALRM returned to which thread? (process
 master or individual child)

On Sun, 11 Apr 2010, Andi Kleen wrote:

> "Frantisek Rysanek" <Frantisek.Rysanek@...t.cz> writes:
> 
> > Yes, it used to be quite a relief to have Linux do the management of 
> > timers for me. Now I have two options to choose from:
> > 1) write my own "timer queueing" (timekeeping) code to order the 
> > timers for me in the master thread
> > 2) find another function, similar to setitimer(), that would function 
> > the way setitimer() used to work in the old days...
> 
> POSIX timers (timer_create et.al.) allow specifying the signal.
> 
> So if you use custom RT signals for each threads and block them in the
> threads you don't want them it should work. This would limit the
> maximum number of threads though because there's only a limited
> range of RT signals.
> 
> There are probably other ways to do this too, e.g. with some clever
> use of timerfd_create in recent kernels.

Definitely timerfd allows you to handle the timer event wherever you 
like, independently from signals.  Much much simpler routing.
But if you need to be compatible with multiple unixes, of even older linux 
kernel, you are out of luck with timerfd.


- Davide


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