linux-kernel - Re: [PATCH v3 1/7] sched: introduce primitives to account for CFS bandwidth tracking

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Date:	Thu, 14 Oct 2010 15:24:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	balbir@...ux.vnet.ibm.com
Cc:	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Dhaval Giani <dhaval.giani@...il.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Avi Kivity <avi@...hat.com>,
	Chris Friesen <cfriesen@...tel.com>,
	Paul Menage <menage@...gle.com>,
	Mike Waychison <mikew@...gle.com>,
	Paul Turner <pjt@...gle.com>, Nikhil Rao <ncrao@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 1/7] sched: introduce primitives to account for CFS
 bandwidth tracking

On Thu, 2010-10-14 at 18:08 +0530, Balbir Singh wrote:
> > > 
> > > hrtimer_start_expires(period_timer, HRTIMER_MODE_ABS_PINNED) if we
> > > don't care about wakeup_softirq, is there a reason we prefer to keep
> > > wakeup as 0?
> > 
> > You cannot do wakeups while holding the rq->lock, can you? :-)
> >
> 
> :-) Yes, given that we wakeup softirq only for the current CPU. There
> is scope for some code reuse anyway, I'll see if I can send a patch. 

Well, both Thomas and I would like hrtimer_start() and friends to return
-ETIME in this case. But that means changing all callers to cope with
that, and sweeping the tree to make that happen is like lots of work.
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