linux-kernel - Re: scheduling hrtimers while holding rq->lock

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Date:	Tue, 29 Jul 2008 22:52:10 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Daniel Rosenthal <danielrosenthal@....org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Ulrich Drepper <drepper@...hat.com>
Subject: Re: scheduling hrtimers while holding rq->lock

On Tue, 2008-07-29 at 15:23 -0400, Daniel Rosenthal wrote:
> What's the best way for scheduling code to start an hrtimer while
> holding the rq->lock?  I am trying to implement SCHED_SPORADIC
> (sporadic server) in the realtime scheduling class (rt_sched_class),
> and it needs to schedule aperiodic, asynchronous replenishment
> operations which are independent of timeslice expiration.  This is to
> implement the functionality that when a SCHED_SPORADIC task blocks or
> uses up its timeslice, one of these asynchronous events is scheduled
> to happen at some time offset in the future that doesn't necessarily
> correspond to any timeslice expiration.
> 
> Is there some way to schedule this event without duplicating the code
> that the generic scheduler currently uses for its hrtick_timer?  As
> in, is there a way to do this without adding a thread flag similar in
> function to TIF_HRTICK_RESCHED and calling an rt_sched_class function
> from do_notify_resume if the flag is set?
> 
> The code snippet below is what I am trying to do.
> 
> Please CC me explicitly in any replies.

Look at .27-rc1 ;-)

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