linux-kernel - Re: [PATCH][RFC] time: add wait_interruptible_timeout macro to sleep (w. timeout) until wake

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Message-ID: <1267461438.5157.9586.camel@thor.local>
Date:	Mon, 01 Mar 2010 17:37:18 +0100
From:	Michel Dänzer <michel@...nzer.net>
To:	Rafał Miłecki <zajec5@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	DRI <dri-devel@...ts.sourceforge.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][RFC] time: add wait_interruptible_timeout macro to
 sleep  (w. timeout) until wake_up

On Sat, 2010-02-27 at 10:33 +0100, Rafał Miłecki wrote: 
> W dniu 26 lutego 2010 20:01 użytkownik Ville Syrjälä <syrjala@....fi> napisał:
> > Disabling the condition check doesn't make sense.
> >
> > You could use a completion.
> >
> > init_completion(vbl_irq);
> > enable_vbl_irq();
> > wait_for_completion(vbl_irq);
> > disable_vbl_irq();
> > and call complete(vbl_irq) in the interrupt handler.
> >
> > The same would of course work with just some flag or counter
> > and a wait queue.
> 
> Ouch, I can see it gone bad already.
> 
> Firstly I simply just wanted to avoid condition in wait_event_*. It
> looked unnecessary as I got interrupts (signals).

So this code runs in user process context? If so, it should return to
userspace ASAP on signal receipt, otherwise e.g. smoothness of X mouse
movement may suffer.

If that's a problem, then maybe the code should run in a different
context, e.g. a tasklet or some kind of worker kernel thread.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer
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