linux-kernel - Re: hrtimer: about hres

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Message-ID: <alpine.LFD.2.00.1005111032200.3401@localhost.localdomain>
Date:	Tue, 11 May 2010 10:33:35 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Iram Shahzad <iram.shahzad@...fujitsu.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: hrtimer: about hres_active

Iram,

please do _NOT_ top post.

On Tue, 11 May 2010, Iram Shahzad wrote:
> > No. The system switches to high resolution mode late in the boot
> > process and it does so only when there is high res capable hardware
> > available.
> 
> So far as I checked, hres_active is set to 1 in hrtimer_switch_to_hres.
> hrtimer_switch_to_hres is only called from hrtimer_run_pending.
> And hrtimer_run_pending is called from timer wheel softirq.
> That is why I concluded that hres_active is set at 1st timer softirq.
> Do you just mean that it is not the 1st softirq, or do you
> mean that in some other place in the late boot process
> there is another code which sets hres_active?

It happens from softirq context, but not from the 1st softirq.
 
> And is it correct that hres_active remains 1 forever once set to it?

Yes. There is no way back.
 
Thanks,

	tglx
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