From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756452Ab0FHUzq (ORCPT ); Tue, 8 Jun 2010 16:55:46 -0400 Received: from hera.kernel.org ([140.211.167.34]:44985 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754655Ab0FHUzo (ORCPT ); Tue, 8 Jun 2010 16:55:44 -0400 Date: Tue, 8 Jun 2010 20:55:13 GMT From: tip-bot for Peter Zijlstra Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, fweisbec@gmail.com, a.p.zijlstra@chello.nl, stable@kernel.org, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, fweisbec@gmail.com, a.p.zijlstra@chello.nl, stable@kernel.org, tglx@linutronix.de, mingo@elte.hu In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf: Fix signed comparison in perf_adjust_period() Message-ID: Git-Commit-ID: f6ab91add6355e231e1c47897027b2a6ee4fa268 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]); Tue, 08 Jun 2010 20:55:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: f6ab91add6355e231e1c47897027b2a6ee4fa268 Gitweb: http://git.kernel.org/tip/f6ab91add6355e231e1c47897027b2a6ee4fa268 Author: Peter Zijlstra AuthorDate: Fri, 4 Jun 2010 15:18:01 +0200 Committer: Ingo Molnar CommitDate: Tue, 8 Jun 2010 18:43:00 +0200 perf: Fix signed comparison in perf_adjust_period() Frederic reported that frequency driven swevents didn't work properly and even caused a division-by-zero error. It turns out there are two bugs, the division-by-zero comes from a failure to deal with that in perf_calculate_period(). The other was more interesting and turned out to be a wrong comparison in perf_adjust_period(). The comparison was between an s64 and u64 and got implicitly converted to an unsigned comparison. The problem is that period_left is typically < 0, so it ended up being always true. Cure this by making the local period variables s64. Reported-by: Frederic Weisbecker Tested-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra Cc: LKML-Reference: Signed-off-by: Ingo Molnar --- kernel/perf_event.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 31d6afe..ff86c55 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1507,6 +1507,9 @@ do { \ divisor = nsec * frequency; } + if (!divisor) + return dividend; + return div64_u64(dividend, divisor); } @@ -1529,7 +1532,7 @@ static int perf_event_start(struct perf_event *event) static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count) { struct hw_perf_event *hwc = &event->hw; - u64 period, sample_period; + s64 period, sample_period; s64 delta; period = perf_calculate_period(event, nsec, count);