Messages in this thread Patch in this message | | | Date | Fri, 16 Feb 2018 01:34:54 -0800 | From | tip-bot for Kan Liang <> | Subject | [tip:perf/urgent] perf mmap: Recalculate size for overwrite mode |
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Commit-ID: dc6c35c679e96987dc83a003f30bc2cc33c84c00 Gitweb: https://git.kernel.org/tip/dc6c35c679e96987dc83a003f30bc2cc33c84c00 Author: Kan Liang <kan.liang@intel.com> AuthorDate: Thu, 18 Jan 2018 13:26:17 -0800 Committer: Arnaldo Carvalho de Melo <acme@redhat.com> CommitDate: Thu, 15 Feb 2018 09:51:57 -0300
perf mmap: Recalculate size for overwrite mode
In perf_mmap__push(), the 'size' need to be recalculated, otherwise the invalid data might be pushed to the record in overwrite mode.
The issue is introduced by commit 7fb4b407a124 ("perf mmap: Don't discard prev in backward mode").
When the ring buffer is full in overwrite mode, backward_rb_find_range() will be called to recalculate the 'start' and 'end'. The 'size' needs to be recalculated accordingly.
Unconditionally recalculate the 'size', not just for full ring buffer in overwrite mode. Because:
- There is no harmful to recalculate the 'size' for other cases. - The code of calculating 'start' and 'end' will be factored out later. The new function does not need to return 'size'.
Signed-off-by: Kan Liang <kan.liang@intel.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Cc: Andi Kleen <ak@linux.intel.com> Cc: Jin Yao <yao.jin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Wang Nan <wangnan0@huawei.com> Fixes: 7fb4b407a124 ("perf mmap: Don't discard prev in backward mode") Link: http://lkml.kernel.org/r/1516310792-208685-3-git-send-email-kan.liang@intel.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> --- tools/perf/util/mmap.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c index 05076e6..97cf4fa 100644 --- a/tools/perf/util/mmap.c +++ b/tools/perf/util/mmap.c @@ -302,6 +302,8 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite, return -1; } + size = end - start; + if ((start & md->mask) + size != (end & md->mask)) { buf = &data[start & md->mask]; size = md->mask + 1 - (start & md->mask);
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