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| author | Vince Weaver <vincent.weaver@maine.edu> | 2016-10-21 00:38:06 -0400 |
|---|---|---|
| committer | Michael Kerrisk <mtk.manpages@gmail.com> | 2016-10-21 08:44:15 +0200 |
| commit | 988688f6067a3327236d9f97fde71e4b8edb399c (patch) | |
| tree | da60c663b9ef25a4f63403b846b80b2a4dda4ab9 | |
| parent | dceb9af608235aca743ccc2423c40c485d950de2 (diff) | |
| download | man-pages-988688f6067a3327236d9f97fde71e4b8edb399c.tar.gz | |
perf_event_open.2: Update time_shift sample code
Linux 4.3 (b20112edeadf0b8a1416de061caa4beb11539902) improved
the accuracy of the clock/ns conversion routines. As a result
the shift factor can now be 32. This value is directly
exported in the perf_event_open() mmap page, and this
potentially breaks the sample code that shifts 1 left by
the shift value.
Add a cast in the sample code so that a proper 64-bit value
results from the shift. This is the same change that was
made to the sample code in include/uapi/linux/perf_event.h
in Linux 4.4 (b9511cd761faafca7a1acc059e792c1399f9d7c6).
Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
| -rw-r--r-- | man2/perf_event_open.2 | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index ae15cc6bc9..fade28cae5 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -1619,7 +1619,7 @@ delta since u64 quot, rem; u64 delta; quot = (cyc >> time_shift); - rem = cyc & ((1 << time_shift) \- 1); + rem = cyc & (((u64)1 << time_shift) \- 1); delta = time_offset + quot * time_mult + ((rem * time_mult) >> time_shift); .fi @@ -1664,7 +1664,7 @@ And vice versa: .nf quot = cyc >> time_shift; - rem = cyc & ((1 << time_shift) - 1); + rem = cyc & (((u64)1 << time_shift) - 1); timestamp = time_zero + quot * time_mult + ((rem * time_mult) >> time_shift); .fi |