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

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Date:	Thu, 17 May 2012 21:56:18 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	David Daney <david.daney@...ium.com>
CC:	Yong Zhang <yong.zhang0@...il.com>, ralf@...ux-mips.org,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/8] patchset focus on MIPS SMP woes

Hello.

On 05/17/2012 08:13 PM, David Daney 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):

    I noted not only change log grammar, also comment grammar. And a missing 
summary in commit reference. :-)

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

WBR, Sergei
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