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perf mmap: Discard 'prev' in perf_mmap__read() 

The 'start' and 'prev' variables are duplicates in perf_mmap__read().

Use 'map->prev' to replace 'start' in perf_mmap__read_*().

Suggested-by: Wang Nan <wangnan0@huawei.com>
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>
Link: http://lkml.kernel.org/r/1516310792-208685-7-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Kan Liang 2018-01-18 13:26:21 -08:00 committed by Arnaldo Carvalho de Melo
parent 189f2cc91f
commit b4b036b4c7
1 changed files with 10 additions and 18 deletions
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28
tools/perf/util/mmap.c
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@ -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 */ /* When check_messup is true, 'end' must points to a good entry */
static union perf_event *perf_mmap__read(struct perf_mmap *map, static union perf_event *perf_mmap__read(struct perf_mmap *map,
u64 start, u64 end, u64 *prev) u64 *startp, u64 end)
{ {
unsigned char *data = map->base + page_size; unsigned char *data = map->base + page_size;
union perf_event *event = NULL; union perf_event *event = NULL;
int diff = end - start; int diff = end - *startp;
if (diff >= (int)sizeof(event->header)) { if (diff >= (int)sizeof(event->header)) {
size_t size; size_t size;
event = (union perf_event *)&data[start & map->mask]; event = (union perf_event *)&data[*startp & map->mask];
size = event->header.size; size = event->header.size;
if (size < sizeof(event->header) || diff < (int)size) { if (size < sizeof(event->header) || diff < (int)size)
event = NULL; return NULL;
goto broken_event;
}
/* /*
* Event straddles the mmap boundary -- header should always * Event straddles the mmap boundary -- header should always
* be inside due to u64 alignment of output. * be inside due to u64 alignment of output.
*/ */
if ((start & map->mask) + size != ((start + size) & map->mask)) { if ((*startp & map->mask) + size != ((*startp + size) & map->mask)) {
unsigned int offset = start; unsigned int offset = *startp;
unsigned int len = min(sizeof(*event), size), cpy; unsigned int len = min(sizeof(*event), size), cpy;
void *dst = map->event_copy; 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; event = (union perf_event *)map->event_copy;
} }
start += size; *startp += size;
} }
broken_event:
if (prev)
*prev = start;
return event; return event;
} }
union perf_event *perf_mmap__read_forward(struct perf_mmap *map) union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
{ {
u64 head; u64 head;
u64 old = map->prev;
/* /*
* Check if event was unmapped due to a POLLHUP/POLLERR. * Check if event was unmapped due to a POLLHUP/POLLERR.
@ -82,13 +75,12 @@ union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
head = perf_mmap__read_head(map); head = perf_mmap__read_head(map);
return perf_mmap__read(map, old, head, &map->prev); return perf_mmap__read(map, &map->prev, head);
} }
union perf_event *perf_mmap__read_backward(struct perf_mmap *map) union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
{ {
u64 head, end; u64 head, end;
u64 start = map->prev;
/* /*
* Check if event was unmapped due to a POLLHUP/POLLERR. * Check if event was unmapped due to a POLLHUP/POLLERR.
@ -118,7 +110,7 @@ union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
else else
end = head + map->mask + 1; end = head + map->mask + 1;
return perf_mmap__read(map, start, end, &map->prev); return perf_mmap__read(map, &map->prev, end);
} }
void perf_mmap__read_catchup(struct perf_mmap *map) void perf_mmap__read_catchup(struct perf_mmap *map)