From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754470Ab3C0NPh (ORCPT ); Wed, 27 Mar 2013 09:15:37 -0400 Received: from 8bytes.org ([85.214.48.195]:47483 "EHLO mail.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753942Ab3C0NPg (ORCPT ); Wed, 27 Mar 2013 09:15:36 -0400 Date: Wed, 27 Mar 2013 14:15:32 +0100 From: Joerg Roedel To: Borislav Petkov , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Stephane Eranian , Namhyung Kim , Jiri Olsa , Peter Zijlstra Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code: asm/8267 Message-ID: <20130327131532.GL30540@8bytes.org> References: <20130324115556.GA4866@pd.tnic> <20130324155924.GB4866@pd.tnic> <20130326183452.GC27518@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130326183452.GC27518@pd.tnic> User-Agent: Mutt/1.5.21 (2010-09-15) X-DSPAM-Result: Whitelisted X-DSPAM-Processed: Wed Mar 27 14:15:34 2013 X-DSPAM-Confidence: 0.9984 X-DSPAM-Probability: 0.0000 X-DSPAM-Signature: 5152f0f623671320318495 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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