From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932753Ab0CKOn2 (ORCPT ); Thu, 11 Mar 2010 09:43:28 -0500 Received: from hera.kernel.org ([140.211.167.34]:35597 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932675Ab0CKOnV (ORCPT ); Thu, 11 Mar 2010 09:43:21 -0500 Date: Thu, 11 Mar 2010 14:41:18 GMT From: tip-bot for Peter Zijlstra Cc: linux-kernel@vger.kernel.org, eranian@google.com, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, eranian@google.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <1268311069.5037.31.camel@laptop> References: <1268311069.5037.31.camel@laptop> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf, x86: Fix hw_perf_enable() event assignment Message-ID: Git-Commit-ID: 45e16a6834b6af098702e5ea6c9a40de42ff77d8 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Thu, 11 Mar 2010 14:41:18 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 45e16a6834b6af098702e5ea6c9a40de42ff77d8 Gitweb: http://git.kernel.org/tip/45e16a6834b6af098702e5ea6c9a40de42ff77d8 Author: Peter Zijlstra AuthorDate: Thu, 11 Mar 2010 13:40:30 +0100 Committer: Ingo Molnar CommitDate: Thu, 11 Mar 2010 15:21:28 +0100 perf, x86: Fix hw_perf_enable() event assignment What happens is that we schedule badly like: <...>-1987 [019] 280.252808: x86_pmu_start: event-46/1300c0: idx: 0 <...>-1987 [019] 280.252811: x86_pmu_start: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252812: x86_pmu_start: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252813: x86_pmu_start: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252814: x86_pmu_start: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252825: x86_pmu_stop: event-46/1300c0: idx: 0 <...>-1987 [019] 280.252826: x86_pmu_stop: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252827: x86_pmu_stop: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252828: x86_pmu_stop: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252829: x86_pmu_stop: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252834: x86_pmu_start: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252834: x86_pmu_start: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252835: x86_pmu_start: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252836: x86_pmu_start: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252837: x86_pmu_start: event-51/1300c0: idx: 32 *FAIL* This happens because we only iterate the n_running events in the first pass, and reset their index to -1 if they don't match to force a re-assignment. Now, in our RR example, n_running == 0 because we fully unscheduled, so event-50 will retain its idx==32, even though in scheduling it will have gotten idx=0, and we don't trigger the re-assign path. The easiest way to fix this is the below patch, which simply validates the full assignment in the second pass. Reported-by: Stephane Eranian Signed-off-by: Peter Zijlstra LKML-Reference: <1268311069.5037.31.camel@laptop> Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_event.c | 12 +++--------- 1 files changed, 3 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c index c6bde7d..5fb490c 100644 --- a/arch/x86/kernel/cpu/perf_event.c +++ b/arch/x86/kernel/cpu/perf_event.c @@ -811,7 +811,6 @@ void hw_perf_enable(void) * step2: reprogram moved events into new counters */ for (i = 0; i < n_running; i++) { - event = cpuc->event_list[i]; hwc = &event->hw; @@ -826,21 +825,16 @@ void hw_perf_enable(void) continue; x86_pmu_stop(event); - - hwc->idx = -1; } for (i = 0; i < cpuc->n_events; i++) { - event = cpuc->event_list[i]; hwc = &event->hw; - if (i < n_running && - match_prev_assignment(hwc, cpuc, i)) - continue; - - if (hwc->idx == -1) + if (!match_prev_assignment(hwc, cpuc, i)) x86_assign_hw_event(event, cpuc, i); + else if (i < n_running) + continue; x86_pmu_start(event); }