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Subject: Re: [PATCH v3 1/7] sched: introduce primitives to account for CFS
 bandwidth tracking
From: Peter Zijlstra <peterz@infradead.org>
To: balbir@linux.vnet.ibm.com
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>, linux-kernel@vger.kernel.org,
        Dhaval Giani <dhaval.giani@gmail.com>,
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        Nikhil Rao <ncrao@google.com>, Thomas Gleixner <tglx@linutronix.de>
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Date: Thu, 14 Oct 2010 15:24:24 +0200
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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.