linux-kernel - Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[

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Date:	Tue, 29 May 2012 13:32:09 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Yong Zhang <yong.zhang0@...il.com>
CC:	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
Subject: Re: [RFC PATCH 00/10] Cleanup ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()

On 05/29/2012 12:45 PM, Yong Zhang wrote:

> As discussed with Srivatsa [1], it seems there is no need to keep
> ipi_call_[un]lock_irq() when cpu bring-up/down. Because:
> 
> 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.
> 
> In short it's more likely that keeping ipi_call_[un]lock() is leftover
> before we introduce generic smp helper. This patchset is just to clean
> things up.
> 
> [1] http://marc.info/?l=linux-kernel&m=133766786814484&w=2
> 
> Yong Zhang (10):
>   hexagon: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   mn10300: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   parisc: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   S390: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   tile: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   x86: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   ia64: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()
>   SPARC: smp: remove call to ipi_call_lock_irq()/ipi_call_unlock_irq()
>   POWERPC: smp: remove call to ipi_call_lock()/ipi_call_unlock()
>   smp: remove ipi_call_lock[_irq]()/ipi_call_unlock[_irq]()
>


All patches except the sparc one look good.
Acked-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>

Regards,
Srivatsa S. Bhat

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