On Thu, Dec 21, 2017 at 10:08:45AM -0800, [email protected] wrote:
> From: Kan Liang <[email protected]>
>
> 'start' and 'prev' are duplicate in perf_mmap__read()
>
> Use 'map->prev' to replace 'start' in perf_mmap__read_*().
>
> Suggested-by: Wang Nan <[email protected]>
> Signed-off-by: Kan Liang <[email protected]>
> ---
> tools/perf/util/mmap.c | 28 ++++++++++------------------
> 1 file changed, 10 insertions(+), 18 deletions(-)
>
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index 3fd4f3c..a844a2f 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -22,29 +22,27 @@ size_t perf_mmap__mmap_len(struct perf_mmap *map)
>
> /* When check_messup is true, 'end' must points to a good entry */
> static union perf_event *perf_mmap__read(struct perf_mmap *map,
> - u64 start, u64 end, u64 *prev)
> + u64 *start, u64 end)
> {
> unsigned char *data = map->base + page_size;
> union perf_event *event = NULL;
> - int diff = end - start;
> + int diff = end - *start;
I'd like more if the arg was pointer, like 'u64 *startp' and you
kept using the 'u64 start' value in the body.. but can't see any
technical benefit behind it to force it ;-)
jirka
>
> if (diff >= (int)sizeof(event->header)) {
> size_t size;
>
> - event = (union perf_event *)&data[start & map->mask];
> + event = (union perf_event *)&data[*start & map->mask];
> size = event->header.size;
>
> - if (size < sizeof(event->header) || diff < (int)size) {
> - event = NULL;
> - goto broken_event;
> - }
> + if (size < sizeof(event->header) || diff < (int)size)
> + return NULL;
>
> /*
> * Event straddles the mmap boundary -- header should always
> * be inside due to u64 alignment of output.
> */
> - if ((start & map->mask) + size != ((start + size) & map->mask))
> {
> - unsigned int offset = start;
> + if ((*start & map->mask) + size != ((*start + size) &
> map->mask)) {
> + unsigned int offset = *start;
> unsigned int len = min(sizeof(*event), size), cpy;
> void *dst = map->event_copy;
>
> @@ -59,20 +57,15 @@ static union perf_event *perf_mmap__read(struct perf_mmap
> *map,
> event = (union perf_event *)map->event_copy;
> }
>
> - start += size;
> + *start += size;
> }
>
> -broken_event:
> - if (prev)
> - *prev = start;
> -
> return event;
> }
SNIP
