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

To: Yong Zhang <yong.zhang0@gmail.com>, ralf@linux-mips.org
Subject: Re: [PATCH 0/8] patchset focus on MIPS SMP woes
From: David Daney <david.daney@cavium.com>
Date: Thu, 17 May 2012 09:13:53 -0700
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org
In-reply-to: <1337249410-7162-1-git-send-email-yong.zhang0@gmail.com>
References: <1337249410-7162-1-git-send-email-yong.zhang0@gmail.com>
Sender: linux-mips-bounce@linux-mips.org
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On 05/17/2012 03:10 AM, Yong Zhang wrote:
From: Yong Zhang<yong.zhang@windriver.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@gmail.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@cavium.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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