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Re: [PATCH] sched: provide scheduler_ipi() callback in response to smp_s

To: Benjamin Herrenschmidt <>
Subject: Re: [PATCH] sched: provide scheduler_ipi() callback in response to smp_send_reschedule()
From: Peter Zijlstra <>
Date: Mon, 17 Jan 2011 21:43:03 +0100
Cc: Richard Henderson <>, Ivan Kokshaysky <>, Matt Turner <>, Russell King <>, Mike Frysinger <>, Mikael Starvik <>, Jesper Nilsson <>, Tony Luck <>, Fenghua Yu <>, Hirokazu Takata <>, Ralf Baechle <>, David Howells <>, Koichi Yasutake <>, Kyle McMartin <>, Helge Deller <>, "James E.J. Bottomley" <>, Paul Mackerras <>, Martin Schwidefsky <>, Heiko Carstens <>,, Paul Mundt <>, "David S. Miller" <>, Chris Metcalf <>, Jeff Dike <>, Thomas Gleixner <>, Ingo Molnar <>, "H. Peter Anvin" <>,, Jeremy Fitzhardinge <>, Konrad Rzeszutek Wilk <>,,,,,,,,,,,,,,,,,,,, Linux-Arch <>
In-reply-to: <1295296310.2148.29.camel@pasglop>
Original-recipient: rfc822;
References: <1295262433.30950.53.camel@laptop> <1295296310.2148.29.camel@pasglop>
On Tue, 2011-01-18 at 07:31 +1100, Benjamin Herrenschmidt wrote:
> Beware of false positive, I've used "fake" reschedule IPIs in the past
> for other things (like kicking a CPU out of sleep state for unrelated
> reasons). Nothing that I know that is upstream today but some of that
> might come back. I'd like to avoid having to add an atomic to know if
> it's a real reschedule, will the scheduler be smart enough to not bother
> with false positives ? 

Yes it can deal with that, some will be for reschedules, some will be
for ttwu tail ends and x86 too uses this ipi for a few random other
things like kicking kvm out of guest context..

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