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

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Date:	Sun, 04 Mar 2007 08:12:17 -0500
From:	Andres Salomon <dilinger@...ian.org>
To:	tglx@...utronix.de
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

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>

View attachment "hrtimer4.patch" of type "text/x-patch" (477 bytes)