Re: [PATCH 01/22] sched: Provide scheduler_ipi() callback in response to smp_send_reschedule()

Frank Rowand
2011-03-11T01:36:49Z

On 03/02/11 09:38, 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.
>
> BenH notes: PowerPC might use this IPI on offline CPUs under rare
> conditions!!
>
> Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
> Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Acked-by: Chris Metcalf <cmetcalf@tilera.com>
> Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> LKML-Reference: <new-submission>
> ---
> arch/alpha/kernel/smp.c | 3 +--
> arch/arm/kernel/smp.c | 5 +----
> 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 | 4 +---
> arch/mips/cavium-octeon/smp.c | 2 ++
> arch/mips/kernel/smtc.c | 2 +-
> arch/mips/mti-malta/malta-int.c | 2 ++
> arch/mips/pmc-sierra/yosemite/smp.c | 4 ++++
> arch/mips/sgi-ip27/ip27-irq.c | 2 ++
> arch/mips/sibyte/bcm1480/smp.c | 7 +++----
> arch/mips/sibyte/sb1250/smp.c | 7 +++----
> arch/mn10300/kernel/smp.c | 5 +----
> arch/parisc/kernel/smp.c | 5 +----
> arch/powerpc/kernel/smp.c | 3 ++-
> arch/s390/kernel/smp.c | 6 +++---
> arch/sh/kernel/smp.c | 2 ++
> arch/sparc/kernel/smp_32.c | 2 +-
> arch/sparc/kernel/smp_64.c | 1 +
> arch/tile/kernel/smp.c | 6 +-----
> arch/um/kernel/smp.c | 2 +-
> arch/x86/kernel/smp.c | 5 ++---
> arch/x86/xen/smp.c | 5 ++---
> include/linux/sched.h | 1 +
> 26 files changed, 60 insertions(+), 49 deletions(-)
>

< snip >

In this patch the tabs turned into spaces. (None of the other
patches have this problem.)

> Index: linux-2.6/arch/sparc/kernel/smp_32.c
> ===================================================================
> --- linux-2.6.orig/arch/sparc/kernel/smp_32.c
> +++ linux-2.6/arch/sparc/kernel/smp_32.c
> @@ -125,7 +125,7 @@ struct linux_prom_registers smp_penguin_
>
> void smp_send_reschedule(int cpu)
> {
> - /* See sparc64 */
> + scheduler_ipi();
> }

If I understand correctly, this is calling scheduler_ipi() on the
cpu that should be sending an IPI, not on the cpu receiving the IPI.
If so, smp_send_reschedule() needs to send an IPI, and the scheduler_ipi()
put in the place where the IPI is processed.

-Frank