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[Xen-devel] Re: [PATCH] sched: provide scheduler_ipi() callback in respo

To: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] sched: provide scheduler_ipi() callback in response to smp_send_reschedule()
From: David Daney <ddaney@xxxxxxxxxxxxxxxxxx>
Date: Mon, 17 Jan 2011 11:18:57 -0800
Cc: linux-m32r-ja@xxxxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Heiko Carstens <heiko.carstens@xxxxxxxxxx>, David Howells <dhowells@xxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, sparclinux@xxxxxxxxxxxxxxx, Linux-Arch <linux-arch@xxxxxxxxxxxxxxx>, linux-s390@xxxxxxxxxxxxxxx, Jesper Nilsson <jesper.nilsson@xxxxxxxx>, Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>, Russell King <linux@xxxxxxxxxxxxxxxx>, Hirokazu Takata <takata@xxxxxxxxxxxxxx>, x86@xxxxxxxxxx, "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, Matt Turner <mattst88@xxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Mike Frysinger <vapier@xxxxxxxxxx>, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Jeff Dike <jdike@xxxxxxxxxxx>, Chris Metcalf <cmetcalf@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Mikael Starvik <starvik@xxxxxxxx>, linux-m32r@xxxxxxxxxxxxxxxxx, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, user-mode-linux-user@xxxxxxxxxxxxxxxxxxxxx, uclinux-dist-devel@xxxxxxxxxxxxxxxxxxxx, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Richard Henderson <rth@xxxxxxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, linux-parisc@xxxxxxxxxxxxxxx, linux-cris-kernel@xxxxxxxx, linux-am33-list@xxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Ralf Baechle <ralf@xxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Kyle McMartin <kyle@xxxxxxxxxxx>, Paul Mundt <lethal@xxxxxxxxxxxx>, linux-alpha@xxxxxxxxxxxxxxx, Martin Schwidefsky <schwidefsky@xxxxxxxxxx>, linux390@xxxxxxxxxx, Koichi Yasutake <yasutake.koichi@xxxxxxxxxxxxxxxx>, linuxppc-dev@xxxxxxxxxxxxxxxx, Helge Deller <deller@xxxxxx>
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On 01/17/2011 03:07 AM, Peter Zijlstra wrote:
For future rework of try_to_wake_up() we'd like to push part of that
onto the CPU the task is actually going to run on, in order to do so we
need a generic callback from the existing scheduler IPI.

This patch introduces such a generic callback: scheduler_ipi() and
implements it as a NOP.

I visited existing smp_send_reschedule() implementations and tried to
add a call to scheduler_ipi() in their handler part, but esp. for MIPS
I'm not quite sure I actually got all of them.

Also, while reading through all this, I noticed the blackfin SMP code
looks to be broken, it simply discards any IPI when low on memory.

Signed-off-by: Peter Zijlstra<a.p.zijlstra@xxxxxxxxx>
  arch/alpha/kernel/smp.c         |    1 +
  arch/arm/kernel/smp.c           |    1 +
  arch/blackfin/mach-common/smp.c |    3 ++-
  arch/cris/arch-v32/kernel/smp.c |   13 ++++++++-----
  arch/ia64/kernel/irq_ia64.c     |    2 ++
  arch/ia64/xen/irq_xen.c         |   10 +++++++++-
  arch/m32r/kernel/smp.c          |    2 +-
  arch/mips/kernel/smtc.c         |    1 +
  arch/mips/sibyte/bcm1480/smp.c  |    7 +++----
  arch/mips/sibyte/sb1250/smp.c   |    7 +++----


You will also have to patch the mailbox_interrupt() function in arch/mips/cavium-octeon/smp.c

David Daney.

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