[tip:perf/core] perf: Fix signed comparison in perf_adjust_period()
in [Kernel]
|
Prev: [tip:x86/uv] x86, UV: Correct BAU regular message type
Next: [tip:x86/uv] x86, UV: BAU structure rearranging
From: tip-bot for Peter Zijlstra on 8 Jun 2010 17:00 Commit-ID: f6ab91add6355e231e1c47897027b2a6ee4fa268 Gitweb: http://git.kernel.org/tip/f6ab91add6355e231e1c47897027b2a6ee4fa268 Author: Peter Zijlstra <a.p.zijlstra(a)chello.nl> AuthorDate: Fri, 4 Jun 2010 15:18:01 +0200 Committer: Ingo Molnar <mingo(a)elte.hu> 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 <fweisbec(a)gmail.com> Tested-by: Frederic Weisbecker <fweisbec(a)gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra(a)chello.nl> Cc: <stable(a)kernel.org> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo(a)elte.hu> --- 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |