From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755637Ab2BBLEI (ORCPT ); Thu, 2 Feb 2012 06:04:08 -0500 Received: from mail-ww0-f44.google.com ([74.125.82.44]:49174 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755575Ab2BBLEG (ORCPT ); Thu, 2 Feb 2012 06:04:06 -0500 Date: Thu, 2 Feb 2012 12:04:01 +0100 From: Stephane Eranian To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, mingo@elte.hu Subject: [PATCH] perf: remove deprecated warn_on_once() Message-ID: <20120202110401.GA30911@quad> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the new throttling/unthrottling code introduced with commit e050e3f, we hit two warn_on_once() in: - intel_pmu_pebs_enable() - intel_pmu_lbr_enable() The assertions are no longer problematic. There is a valid path where they can trigger but it is harmless. The assertion can be triggered with: $ perf record -e instructions:pp .... Leading to paths: intel_pmu_pebs_enable intel_pmu_enable_event x86_perf_event_set_period x86_pmu_start perf_adjust_freq_unthr_context perf_event_task_tick scheduler_tick And: intel_pmu_lbr_enable intel_pmu_enable_event x86_perf_event_set_period x86_pmu_start perf_adjust_freq_unthr_context. perf_event_task_tick scheduler_tick cpuc->enabled is always on because when we get to perf_adjust_freq_unthr_context() the PMU is not totally disabled. Furthermore when we need to adjust a period, we only stop the event we need to change and not the entire PMU. Thus, when we re-enable, cpuc->enabled is already set. Note that when we stop the event, both pebs and lbr are stopped if necessary (and possible). Signed-off-by: Stephane Eranian --- diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c index 73da6b6..d6bd49f 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_ds.c +++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c @@ -439,7 +439,6 @@ void intel_pmu_pebs_enable(struct perf_event *event) hwc->config &= ~ARCH_PERFMON_EVENTSEL_INT; cpuc->pebs_enabled |= 1ULL << hwc->idx; - WARN_ON_ONCE(cpuc->enabled); if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1) intel_pmu_lbr_enable(event); diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index 3fab3de..47a7e63 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -72,8 +72,6 @@ void intel_pmu_lbr_enable(struct perf_event *event) if (!x86_pmu.lbr_nr) return; - WARN_ON_ONCE(cpuc->enabled); - /* * Reset the LBR stack if we changed task context to * avoid data leaks.