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SubjectRe: [PATCH v4 07/11] perf auxtrace: Remove auxtrace_mmap__read_snapshot_head()
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On 11/07/21 1:41 pm, Leo Yan wrote:
> Since the function auxtrace_mmap__read_snapshot_head() is exactly same
> with auxtrace_mmap__read_head(), whether the session is in snapshot mode
> or not, it's unified to use function auxtrace_mmap__read_head() for
> reading AUX buffer head.
>
> And the function auxtrace_mmap__read_snapshot_head() is unused so this
> patch removes it.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> tools/perf/util/auxtrace.c | 5 ++---
> tools/perf/util/auxtrace.h | 10 ----------
> 2 files changed, 2 insertions(+), 13 deletions(-)
>
> diff --git a/tools/perf/util/auxtrace.c b/tools/perf/util/auxtrace.c
> index cb19669d2a5b..7958e17229ea 100644
> --- a/tools/perf/util/auxtrace.c
> +++ b/tools/perf/util/auxtrace.c
> @@ -1686,13 +1686,12 @@ static int __auxtrace_mmap__read(struct mmap *map,
> union perf_event ev;
> void *data1, *data2;
>
> + head = auxtrace_mmap__read_head(mm);
> +
> if (snapshot) {
> - head = auxtrace_mmap__read_snapshot_head(mm);
> if (auxtrace_record__find_snapshot(itr, mm->idx, mm, data,
> &head, &old))

That leaves a nested 'if' which is not kernel style i.e. could be

if (snapshot &&
auxtrace_record__find_snapshot(itr, mm->idx, mm, data, &head, &old))


> return -1;
> - } else {
> - head = auxtrace_mmap__read_head(mm);
> }
>
> if (old == head)
> diff --git a/tools/perf/util/auxtrace.h b/tools/perf/util/auxtrace.h
> index 4f9176368134..d68a5e80b217 100644
> --- a/tools/perf/util/auxtrace.h
> +++ b/tools/perf/util/auxtrace.h
> @@ -440,16 +440,6 @@ struct auxtrace_cache;
>
> #ifdef HAVE_AUXTRACE_SUPPORT
>
> -static inline u64 auxtrace_mmap__read_snapshot_head(struct auxtrace_mmap *mm)
> -{
> - struct perf_event_mmap_page *pc = mm->userpg;
> - u64 head = READ_ONCE(pc->aux_head);
> -
> - /* Ensure all reads are done after we read the head */
> - smp_rmb();
> - return head;
> -}
> -
> static inline u64 auxtrace_mmap__read_head(struct auxtrace_mmap *mm)
> {
> struct perf_event_mmap_page *pc = mm->userpg;
>

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