linux-kernel - Re: [PATCH 0/8] patchset focus on MIPS SMP woes

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Date:	Thu, 17 May 2012 09:13:53 -0700
From:	David Daney <david.daney@...ium.com>
To:	Yong Zhang <yong.zhang0@...il.com>, ralf@...ux-mips.org
CC:	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] patchset focus on MIPS SMP woes

On 05/17/2012 03:10 AM, Yong Zhang wrote:
> From: Yong Zhang<yong.zhang@...driver.com>
>
> Since commit 5fbd036b [sched: Cleanup cpu_active madness] and
> commit 2baab4e9 [sched: Fix select_fallback_rq() vs cpu_active/cpu_online],
> it's more safe to put notify_cpu_starting() and set_cpu_online() with
> irq disabled, otherwise we will have a typical race condition which
> above two commits try to resolve:
>
>        CPU1                            CPU2
> __cpu_up();
>     mp_ops->boot_secondary();
>                                start_secondary();
>                                  ->init_secondary();
>                                    local_irq_enable();
>                                <IRQ>
>                                do something;
>                                      wake up softirqd;
>                                      try_to_wake_up();
>                                        select_fallback_rq();
>                                        /* select wrong cpu */
>     set_cpu_online();
>
>
> This patchset fix the above issue as well as set_cpu_online is
> called on the caller cpu.
>
> BTW, I'm only running it on Cavium board because of limited source,
> so if anyone is interested to test it on other board, that's great :)
>
> Signed-off-by: Yong Zhang<yong.zhang0@...il.com>
>
> Yong Zhang (8):
>    MIPS: Octeon: delay enable irq to ->smp_finish()
>    MIPS: BMIPS: delay irq enable to ->smp_finish()
>    MIPS: SMTC: delay irq enable to ->smp_finish()
>    MIPS: Yosemite: delay irq enable to ->smp_finish()
>    MIPS: call ->smp_finish() a little late
>    MIPS: call set_cpu_online() on the uping cpu with irq disabled
>    MIPS: smp: Warn on too early irq enable
>    MIPS: sync-r4k: remove redundant irq operation
>

This entire patch set (modulo the change log grammar items noted by Sergei):

Acked-by: David Daney <david.daney@...ium.com>


>   arch/mips/cavium-octeon/smp.c       |    2 +-
>   arch/mips/kernel/smp-bmips.c        |   14 +++++++-------
>   arch/mips/kernel/smp.c              |   12 +++++++++---
>   arch/mips/kernel/smtc.c             |    3 ++-
>   arch/mips/kernel/sync-r4k.c         |    5 -----
>   arch/mips/pmc-sierra/yosemite/smp.c |    2 +-
>   6 files changed, 20 insertions(+), 18 deletions(-)
>
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