From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932241AbZDHNGR (ORCPT ); Wed, 8 Apr 2009 09:06:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765346AbZDHNDe (ORCPT ); Wed, 8 Apr 2009 09:03:34 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:54120 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765328AbZDHNDd (ORCPT ); Wed, 8 Apr 2009 09:03:33 -0400 Message-Id: <20090408130408.681326666@chello.nl> References: <20090408130124.715559390@chello.nl> User-Agent: quilt/0.46-1 Date: Wed, 08 Apr 2009 15:01:25 +0200 From: Peter Zijlstra To: Ingo Molnar Cc: Paul Mackerras , Corey Ashford , linux-kernel@vger.kernel.org, Peter Zijlstra Subject: [PATCH 1/9] perf_counter: fix NMI race in task clock Content-Disposition: inline; filename=perf_counter-task-clock-read.patch X-Bad-Reply: References but no 'Re:' in Subject. Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We should not be updating ctx->time from NMI context, work around that. Signed-off-by: Peter Zijlstra --- kernel/perf_counter.c | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) Index: linux-2.6/kernel/perf_counter.c =================================================================== --- linux-2.6.orig/kernel/perf_counter.c +++ linux-2.6/kernel/perf_counter.c @@ -319,8 +319,6 @@ static void __perf_counter_disable(void spin_lock_irqsave(&ctx->lock, flags); - update_context_time(ctx); - /* * If the counter is on, turn it off. * If it is in error state, leave it in error state. @@ -2335,13 +2333,11 @@ static const struct hw_perf_counter_ops * Software counter: task time clock */ -static void task_clock_perf_counter_update(struct perf_counter *counter) +static void task_clock_perf_counter_update(struct perf_counter *counter, u64 now) { - u64 prev, now; + u64 prev; s64 delta; - now = counter->ctx->time; - prev = atomic64_xchg(&counter->hw.prev_count, now); delta = now - prev; atomic64_add(delta, &counter->count); @@ -2369,13 +2365,24 @@ static int task_clock_perf_counter_enabl static void task_clock_perf_counter_disable(struct perf_counter *counter) { hrtimer_cancel(&counter->hw.hrtimer); - task_clock_perf_counter_update(counter); + task_clock_perf_counter_update(counter, counter->ctx->time); + } static void task_clock_perf_counter_read(struct perf_counter *counter) { - update_context_time(counter->ctx); - task_clock_perf_counter_update(counter); + u64 time; + + if (!in_nmi()) { + update_context_time(counter->ctx); + time = counter->ctx->time; + } else { + u64 now = perf_clock(); + u64 delta = now - counter->ctx->timestamp; + time = counter->ctx->time + delta; + } + + task_clock_perf_counter_update(counter, time); } static const struct hw_perf_counter_ops perf_ops_task_clock = { --