From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri, 4 Jun 2010 13:18:01 +0000 (+0200)
Subject: perf: Fix signed comparison in perf_adjust_period()
X-Git-Tag: v2.6.35-rc3~13^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f6ab91add6355e231e1c47897027b2a6ee4fa268;p=pandora-kernel.git

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>
---

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