From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760092Ab3CZSfA (ORCPT ); Tue, 26 Mar 2013 14:35:00 -0400 Received: from mail.skyhub.de ([78.46.96.112]:45521 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750977Ab3CZSe6 (ORCPT ); Tue, 26 Mar 2013 14:34:58 -0400 Date: Tue, 26 Mar 2013 19:34:52 +0100 From: Borislav Petkov To: Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Stephane Eranian Cc: Namhyung Kim , Jiri Olsa , Peter Zijlstra Subject: Re: BUG: using smp_processor_id() in preemptible [00000000] code: asm/8267 Message-ID: <20130326183452.GC27518@pd.tnic> Mail-Followup-To: Borislav Petkov , Ingo Molnar , Peter Zijlstra , Arnaldo Carvalho de Melo , lkml , Stephane Eranian , Namhyung Kim , Jiri Olsa , Peter Zijlstra References: <20130324115556.GA4866@pd.tnic> <20130324155924.GB4866@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20130324155924.GB4866@pd.tnic> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 24, 2013 at 04:59:24PM +0100, Borislav Petkov wrote: > On Sun, Mar 24, 2013 at 12:55:56PM +0100, Borislav Petkov wrote: > > Hi, > > > > so I was tracing a small .c program like so: > > > > $ ./perf record ~/test/asm > > > > and here's what got spewed in dmesg. Kernel is plain -rc4. Any pending > > fixes in tip I should try? > > > > [ 3700.194208] BUG: using smp_processor_id() in preemptible [00000000] code: asm/8333 > > [ 3700.194226] caller is perf_event_task_ctx+0x55/0x140 > > Ok, here's the call stack I was able to reconstruct: > > perf_event_exit_task() > |->perf_event_exit_task_context() > |-> perf_event_task() > |-> perf_event_task_event() > |-> perf_event_task_ctx() > |-> perf_event_task_match() > |-> event_filter_match() > |-> smp_processor_id() -> debug_smp_processor_id() Ok, jolsa just rootcaused it: It is caused by d610d98b5de6860feb21539726e9af7c9094151c calling perf_event_task_ctx() outside of the preempt-safe protection. There's a straightforward fix below, what to people think? -- 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(); } -- Regards/Gruss, Boris. Sent from a fat crate under my desk. Formatting is fine. --