From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753821Ab3K0Nz3 (ORCPT ); Wed, 27 Nov 2013 08:55:29 -0500 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:55057 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750953Ab3K0NzY (ORCPT ); Wed, 27 Nov 2013 08:55:24 -0500 From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Vince Weaver , Will Deacon Subject: [PATCH 1/2] perf: fix PERF_EVENT_IOC_PERIOD to force-reset the period Date: Wed, 27 Nov 2013 13:54:38 +0000 Message-Id: <1385560479-11014-1-git-send-email-will.deacon@arm.com> X-Mailer: git-send-email 1.8.2.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Vince Weaver reports that, on all architectures apart from ARM, PERF_EVENT_IOC_PERIOD doesn't actually update the period until the next event fires. This is counter-intuitive behaviour and is better dealt with in the core code. This patch ensures that the period is forcefully reset when dealing with such a request in the core code. A subsequent patch removes the equivalent hack from the ARM back-end. Cc: Vince Weaver Cc: Peter Zijlstra Signed-off-by: Will Deacon --- Peter -- I didn't want this to get lost, so I picked it up, fixed a typo and wrote a commit message. Could I add your SoB please? Cheers, Will kernel/events/core.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index d724e7757cd1..1c626b923ddf 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3527,7 +3527,7 @@ static void perf_event_for_each(struct perf_event *event, static int perf_event_period(struct perf_event *event, u64 __user *arg) { struct perf_event_context *ctx = event->ctx; - int ret = 0; + int ret = 0, active; u64 value; if (!is_sampling_event(event)) @@ -3551,6 +3551,20 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg) event->attr.sample_period = value; event->hw.sample_period = value; } + + active = (event->state == PERF_EVENT_STATE_ACTIVE); + if (active) { + perf_pmu_disable(ctx->pmu); + event->pmu->stop(event, PERF_EF_UPDATE); + } + + local64_set(&event->hw.period_left, 0); + + if (active) { + event->pmu->start(event, PERF_EF_RELOAD); + perf_pmu_enable(ctx->pmu); + } + unlock: raw_spin_unlock_irq(&ctx->lock); -- 1.8.2.2