linux-kernel - Re: [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock

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Date:	Tue, 29 May 2012 04:36:30 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	yong.zhang0@...il.com
Cc:	srivatsa.bhat@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	ralf@...ux-mips.org, sshtylyov@...sta.com, david.daney@...ium.com,
	nikunj@...ux.vnet.ibm.com, paulmck@...ux.vnet.ibm.com,
	axboe@...nel.dk, mingo@...nel.org, tglx@...utronix.de,
	peterz@...radead.org, akpm@...ux-foundation.org,
	sparclinux@...r.kernel.org
Subject: Re: [UPDATED] [RFC PATCH 08/10] SPARC: smp: remove call to
 ipi_call_lock_irq()/ipi_call_unlock_irq()

From: Yong Zhang <yong.zhang0@...il.com>
Date: Tue, 29 May 2012 16:27:33 +0800

> From: Yong Zhang <yong.zhang@...driver.com>
> Date: Tue, 29 May 2012 12:56:08 +0800
> Subject: [UPDATED] [RFC PATCH 8/10] SPARC: smp: remove call to
>  ipi_call_lock_irq()/ipi_call_unlock_irq()
> 
> 1) call_function.lock used in smp_call_function_many() is just to protect
>    call_function.queue and &data->refs, cpu_online_mask is outside of the
>    lock. And it's not necessary to protect cpu_online_mask,
>    because data->cpumask is pre-calculate and even if a cpu is brougt up
>    when calling arch_send_call_function_ipi_mask(), it's harmless because
>    validation test in generic_smp_call_function_interrupt() will take care
>    of it.
> 
> 2) For cpu down issue, stop_machine() will guarantee that no concurrent
>    smp_call_fuction() is processing.
> 
> And also delay irq enable to after set_cpu_online().
> 
> Signed-off-by: Yong Zhang <yong.zhang0@...il.com>

Acked-by: David S. Miller <davem@...emloft.net>
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