> 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 ;-)
>
I will rename it as startp in V4.
Thanks,
Kan
> 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
