From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756229Ab3C0GCO (ORCPT ); Wed, 27 Mar 2013 02:02:14 -0400 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:50414 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754564Ab3C0GCN (ORCPT ); Wed, 27 Mar 2013 02:02:13 -0400 X-AuditID: 9c93016f-b7cecae000004cf8-bd-51528b63a394 From: Namhyung Kim To: Borislav Petkov Cc: 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 References: <20130324115556.GA4866@pd.tnic> <20130324155924.GB4866@pd.tnic> <20130326183452.GC27518@pd.tnic> Date: Wed, 27 Mar 2013 15:02:10 +0900 In-Reply-To: <20130326183452.GC27518@pd.tnic> (Borislav Petkov's message of "Tue, 26 Mar 2013 19:34:52 +0100") Message-ID: <87ip4dgz31.fsf@sejong.aot.lge.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Borislav, On Tue, 26 Mar 2013 19:34:52 +0100, Borislav Petkov wrote: > 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. Oops, my bad. Forgot to enable CONFIG_DEBUG_PREEMPT when testing. :( > > There's a straightforward fix below, what to people think? Looks okay to me. Thanks for fixing this! Namhyung > > -- > 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(); > }