From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:55861 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751474AbcDQM4X (ORCPT ); Sun, 17 Apr 2016 08:56:23 -0400 Subject: Patch "perf: Cure event->pending_disable race" has been added to the 3.14-stable tree To: peterz@infradead.org, acme@redhat.com, alexander.shishkin@linux.intel.com, gregkh@linuxfoundation.org, jolsa@redhat.com, mingo@kernel.org, tglx@linutronix.de, torvalds@linux-foundation.org Cc: , From: Date: Sun, 17 Apr 2016 05:15:28 -0700 Message-ID: <1460895328240238@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled perf: Cure event->pending_disable race to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: perf-cure-event-pending_disable-race.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 28a967c3a2f99fa3b5f762f25cb2a319d933571b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Wed, 24 Feb 2016 18:45:46 +0100 Subject: perf: Cure event->pending_disable race 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--; Patches currently in stable-queue which might be from peterz@infradead.org are queue-3.14/perf-cure-event-pending_disable-race.patch