linux-kernel - Re: [PATCH -mm] oprofile: BUG: using smp_processor

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Date:	Mon, 22 Sep 2008 12:25:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrea Righi <righi.andrea@...il.com>
Cc:	robert.richter@....com, akpm@...ux-foundation.org,
	oprofile-list@...ts.sf.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] oprofile: BUG: using smp_processor_id() in
	preemptible code


* Andrea Righi <righi.andrea@...il.com> wrote:

> Add local_irq_save() / local_irq_restore() before setting per cpu 
> variable switch_index, to avoid the following BUG:

that just papers over the bug:

> +	local_irq_save(flags);
>  	__get_cpu_var(switch_index) = 0;
> +	local_irq_restore(flags);

either use __raw_get_cpu_var() if we are for sure not preemptible here, 
or fix the preemption status of this codepath.

	Ingo
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