linux-kernel - Re: [v3 PATCH 2/4] timers: Identifying the existing pinned timers

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Message-ID: <20090318043650.GA7138@linux.vnet.ibm.com>
Date:	Wed, 18 Mar 2009 10:06:50 +0530
From:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	a.p.zijlstra@...llo.nl, ego@...ibm.com, mingo@...e.hu,
	andi@...stfloor.org, venkatesh.pallipadi@...el.com,
	vatsa@...ux.vnet.ibm.com, arjan@...radead.org,
	svaidy@...ux.vnet.ibm.com
Subject: Re: [v3 PATCH 2/4] timers: Identifying the existing pinned timers

* Thomas Gleixner <tglx@...utronix.de> [2009-03-17 14:07:44]:

> On Mon, 16 Mar 2009, Arun R Bharadwaj wrote:
> > * Arun R Bharadwaj <arun@...ux.vnet.ibm.com> [2009-03-16 16:40:45]:
> > 
> > The following pinned hrtimers have been identified and marked:
> > 1)sched_rt_period_timer
> > 2)tick_sched_timer
> > 3)stack_trace_timer_fn
> 
> How did you verify that these are the only timers which need to be
> pinned ?
>

Until 2.6.28, there was a callback mode called HRTIMER_CB_IRQSAFE_PERCPU
which did not allow timers to be migrated, if set.
These were the only 3 hrtimers which were using that callback mode.

--arun

> Can we be sure that there is no code which relies on the current
> behaviour to keep functionality tied together ? Networking and block
> layer comes to mind.
> 
> Thanks,
> 
> 	tglx
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