diff options
| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2010-06-04 15:18:01 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-07-05 11:16:07 -0700 |
| commit | e26e13a7e153ae645a430c4983241b0e9987d5cf (patch) | |
| tree | 52d915da4d749839c485ebe7e2b4e2c72b17427d /kernel | |
| parent | 402d655a0d2df775bfcf345fcc19db8a32b3a1c8 (diff) | |
perf: Fix signed comparison in perf_adjust_period()
commit f6ab91add6355e231e1c47897027b2a6ee4fa268 upstream.
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@gmail.com>
Tested-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'kernel')
| -rw-r--r-- | 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 f3a7003eb5c..fbbe79bf4ef 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1417,13 +1417,16 @@ do { \ divisor = nsec * frequency; } + if (!divisor) + return dividend; + return div64_u64(dividend, divisor); } 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); |