Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752676AbcDRDqR (ORCPT ); Sun, 17 Apr 2016 23:46:17 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:35386 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752225AbcDRC1N (ORCPT ); Sun, 17 Apr 2016 22:27:13 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alexander Shishkin , "Peter Zijlstra (Intel)" , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Thomas Gleixner , dvyukov@google.com, eranian@google.com, oleg@redhat.com, panand@redhat.com, sasha.levin@oracle.com, vince@deater.net, Ingo Molnar Subject: [PATCH 3.14 30/37] perf: Cure event->pending_disable race Date: Mon, 18 Apr 2016 11:26:02 +0900 Message-Id: <20160418022402.341031330@linuxfoundation.org> X-Mailer: git-send-email 2.8.0 In-Reply-To: <20160418022400.661946311@linuxfoundation.org> References: <20160418022400.661946311@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2199 Lines: 67 3.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra commit 28a967c3a2f99fa3b5f762f25cb2a319d933571b upstream. Because event_sched_out() checks event->pending_disable _before_ actually disabling the event, it can happen that the event fires after it checks but before it gets disabled. This would leave event->pending_disable set and the queued irq_work will try and process it. However, if the event trigger was during schedule(), the event might have been de-scheduled by the time the irq_work runs, and perf_event_disable_local() will fail. Fix this by checking event->pending_disable _after_ we call event->pmu->del(). This depends on the latter being a compiler barrier, such that the compiler does not lift the load and re-creates the problem. Tested-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dvyukov@google.com Cc: eranian@google.com Cc: oleg@redhat.com Cc: panand@redhat.com Cc: sasha.levin@oracle.com Cc: vince@deater.net Link: http://lkml.kernel.org/r/20160224174948.040469884@infradead.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- kernel/events/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -1400,14 +1400,14 @@ event_sched_out(struct perf_event *event perf_pmu_disable(event->pmu); + event->tstamp_stopped = tstamp; + event->pmu->del(event, 0); + event->oncpu = -1; event->state = PERF_EVENT_STATE_INACTIVE; if (event->pending_disable) { event->pending_disable = 0; event->state = PERF_EVENT_STATE_OFF; } - event->tstamp_stopped = tstamp; - event->pmu->del(event, 0); - event->oncpu = -1; if (!is_software_event(event)) cpuctx->active_oncpu--;