linux-kernel - Re: [PATCH 1 of 6] x86, UV: smp_processor

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Message-ID: <4DF8EA26.2000301@zytor.com>
Date:	Wed, 15 Jun 2011 10:21:42 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Cliff Wickman <cpw@....com>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1 of 6] x86, UV: smp_processor_id in a preemptable	region

On 06/15/2011 09:40 AM, Cliff Wickman wrote:
> 
> So would you say I should really widen the scope of the non-preemptible
> region to include everything done with the results of that call to
> smp_processor_id()?  
> Which in this case is the call to parse_tunables_write().
> Like this:
> 
>         preempt_disable();
>         bcp = &per_cpu(bau_control, smp_processor_id());
> 
>         ret = parse_tunables_write(bcp, instr, count);
>         preempt_enable_no_resched();
> 

Funny enough, this is such a common pattern that we have helpers for it.
We call this get_cpu() ... put_cpu().

	-hpa

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