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swh:1:snp:32555a3fd8878f019c2ebd6c964bc1edcaeff337
Revision f6ab91add6355e231e1c47897027b2a6ee4fa268 authored by Peter Zijlstra on 04 June 2010, 13:18:01 UTC, committed by Ingo Molnar on 08 June 2010, 16:43:00 UTC 
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>
1 parent 58cc1a9
History
Tip revision: ffb4d94b4314655cea60ab7962756e6bab72fc7e authored by Linus Torvalds on 30 September 2022, 23:25:52 UTC
Merge tag 'drm-fixes-2022-10-01' of git://anongit.freedesktop.org/drm/drm
Tip revision: ffb4d94
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