linux-kernel - Re: [PATCH] highres: Do not run the TIMER_SOFTIRQ after switching to highres mode

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Message-Id: <1173014630.24738.132.camel@localhost.localdomain>
Date:	Sun, 04 Mar 2007 14:23:50 +0100
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andres Salomon <dilinger@...ian.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] highres: Do not run the TIMER_SOFTIRQ after switching
	to	highres mode

On Sun, 2007-03-04 at 08:12 -0500, Andres Salomon wrote:
> Thomas Gleixner wrote:
> >>> The question is, how the tick timer gets enqueued in the softirq queue.
> >>> Can you isolate the codepath, where this happens ?
> > 
> > The TIMER_SOFTIRQ runs the hrtimers during bootup until a usable
> > clocksource and clock event sources are registered. The switch to high
> > resolution mode happens inside of the TIMER_SOFTIRQ, but runs the
> > softirq afterwards. That way the tick emulation timer, which was set up
> > in the switch to highres might be executed in the softirq context, which
> > is a BUG. The rbtree has not to be touched by the softirq after the
> > highres switch.
> > 
> 
> And an additional request, just to make it explicit that we should not
> have any NO_SOFTIRQ callbacks in the tree; BUG out if we encounter such
> a thing.
> 
> Signed-off-by: Andres Salomon <dilinger@...ian.org>

Acked-by: Thomas Gleixner <tglx@...utronix.de>


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