linux-kernel - Re: BUG: using smp_processor_id() in preemptible [00000000] code: asm/8267

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Message-ID: <20130327131532.GL30540@8bytes.org>
Date:	Wed, 27 Mar 2013 14:15:32 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code:
 asm/8267

On Tue, Mar 26, 2013 at 07:34:52PM +0100, Borislav Petkov wrote:
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 7b4a55d41efc..f3bb3384a106 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4455,8 +4455,11 @@ static void perf_event_task_event(struct perf_task_event *task_event)
>  next:
>  		put_cpu_ptr(pmu->pmu_cpu_context);
>  	}
> +
> +	preempt_disable();
>  	if (task_event->task_ctx)
>  		perf_event_task_ctx(task_event->task_ctx, task_event);
> +	preempt_enable();
>  
>  	rcu_read_unlock();
>  }

What makes me wonder here is that the code is preemptible in an
rcu_read_locked section. As far as I know preemption needs to be
disabled while holding the rcu_read_lock().


	Joerg


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