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

To: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] sched: provide scheduler_ipi() callback in response to smp_send_reschedule()
From: David Daney <ddaney@caviumnetworks.com>
Date: Mon, 17 Jan 2011 11:18:57 -0800
Cc: Richard Henderson <rth@twiddle.net>, Ivan Kokshaysky <ink@jurassic.park.msu.ru>, Matt Turner <mattst88@gmail.com>, Russell King <linux@arm.linux.org.uk>, Mike Frysinger <vapier@gentoo.org>, Mikael Starvik <starvik@axis.com>, Jesper Nilsson <jesper.nilsson@axis.com>, Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>, Hirokazu Takata <takata@linux-m32r.org>, Ralf Baechle <ralf@linux-mips.org>, David Howells <dhowells@redhat.com>, Koichi Yasutake <yasutake.koichi@jp.panasonic.com>, Kyle McMartin <kyle@mcmartin.ca>, Helge Deller <deller@gmx.de>, "James E.J. Bottomley" <jejb@parisc-linux.org>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>, linux390@de.ibm.com, Paul Mundt <lethal@linux-sh.org>, "David S. Miller" <davem@davemloft.net>, Chris Metcalf <cmetcalf@tilera.com>, Jeff Dike <jdike@addtoit.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org, Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, uclinux-dist-devel@blackfin.uclinux.org, linux-cris-kernel@axis.com, linux-ia64@vger.kernel.org, linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org, linux-mips@linux-mips.org, linux-am33-list@redhat.com, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net, user-mode-linux-user@lists.sourceforge.net, xen-devel@lists.xensource.com, virtualization@lists.osdl.org, Linux-Arch <linux-arch@vger.kernel.org>
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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@chello.nl>
---
  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 +++----
[...]

Peter,

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

David Daney.

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