tree 74dffdf3b78c290d38a78b73788dce64e4c1e857
parent 58cc1a9e3b11a84e66c4d3a4cc9073f2cb0ecabb
author Peter Zijlstra <a.p.zijlstra@chello.nl> 1275657481 +0200
committer Ingo Molnar <mingo@elte.hu> 1276015380 +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@gmail.com>
Tested-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: <stable@kernel.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>