From patchwork Wed Jun 29 18:03:08 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Will Deacon X-Patchwork-Id: 929852 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter2.kernel.org (8.14.4/8.14.4) with ESMTP id p5TI3WG3004117 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Wed, 29 Jun 2011 18:03:53 GMT Received: from canuck.infradead.org ([2001:4978:20e::1]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1Qbz6f-0004cO-2T; Wed, 29 Jun 2011 18:03:21 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Qbz6e-000400-OY; Wed, 29 Jun 2011 18:03:20 +0000 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1Qbz6b-0003zh-B2 for linux-arm-kernel@lists.infradead.org; Wed, 29 Jun 2011 18:03:18 +0000 Received: from localhost.localdomain (e102144-lin.cambridge.arm.com [10.1.69.60]) by cam-admin0.cambridge.arm.com (8.12.6/8.12.6) with ESMTP id p5TI0dY3028101; Wed, 29 Jun 2011 19:00:39 +0100 (BST) From: Will Deacon To: linux-arm-kernel@lists.infradead.org Subject: [PATCH] ARM: perf: do not start the PMU when no events are present Date: Wed, 29 Jun 2011 19:03:08 +0100 Message-Id: <1309370588-30537-1-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 1.7.0.4 MIME-Version: 1.0 Content-Disposition: inline X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.7.6 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110629_140317_638667_DC93D9B8 X-CRM114-Status: GOOD ( 15.26 ) X-Spam-Score: -0.0 (/) X-Spam-Report: SpamAssassin version 3.3.1 on canuck.infradead.org summary: Content analysis details: (-0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 T_RP_MATCHES_RCVD Envelope sender domain matches handover relay domain Cc: Will Deacon X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter2.kernel.org [140.211.167.43]); Wed, 29 Jun 2011 18:03:53 +0000 (UTC) armpmu_enable can be called in situations where no events are present (for example, from the event rotation tick after a profiled task has exited). In this case, we currently start the PMU anyway which may leave it active inevitably without any events being monitored. This patch adds a simple check to the enabling code so that we avoid starting the PMU when no events are present. Reported-by: Ashwin Chaugle Signed-off-by: Will Deacon --- arch/arm/kernel/perf_event.c | 6 ++++-- 1 files changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index d53c0ab..2b5b142 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -583,7 +583,7 @@ static int armpmu_event_init(struct perf_event *event) static void armpmu_enable(struct pmu *pmu) { /* Enable all of the perf events on hardware. */ - int idx; + int idx, enabled = 0; struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); if (!armpmu) @@ -596,9 +596,11 @@ static void armpmu_enable(struct pmu *pmu) continue; armpmu->enable(&event->hw, idx); + enabled = 1; } - armpmu->start(); + if (enabled) + armpmu->start(); } static void armpmu_disable(struct pmu *pmu)