1 files changed, 25 insertions, 48 deletions

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 9fe5f9c7d577..05076e683938 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -21,33 +21,13 @@ 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, bool check_messup,
+static union perf_event *perf_mmap__read(struct perf_mmap *map,
                                          u64 start, u64 end, u64 *prev)
 {
         unsigned char *data = map->base + page_size;
         union perf_event *event = NULL;
         int diff = end - start;
 
-        if (check_messup) {
-                /*
-                 * If we're further behind than half the buffer, there's a chance
-                 * the writer will bite our tail and mess up the samples under us.
-                 *
-                 * If we somehow ended up ahead of the 'end', we got messed up.
-                 *
-                 * In either case, truncate and restart at 'end'.
-                 */
-                if (diff > map->mask / 2 || diff < 0) {
-                        fprintf(stderr, "WARNING: failed to keep up with mmap data.\n");
-
-                        /*
-                         * 'end' points to a known good entry, start there.
-                         */
-                        start = end;
-                        diff = 0;
-                }
-        }
-
         if (diff >= (int)sizeof(event->header)) {
                 size_t size;
 
@@ -89,7 +69,7 @@ broken_event:
         return event;
 }
 
-union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_messup)
+union perf_event *perf_mmap__read_forward(struct perf_mmap *map)
 {
         u64 head;
         u64 old = map->prev;
@@ -102,7 +82,7 @@ union perf_event *perf_mmap__read_forward(struct perf_mmap *map, bool check_mess
 
         head = perf_mmap__read_head(map);
 
-        return perf_mmap__read(map, check_messup, old, head, &map->prev);
+        return perf_mmap__read(map, old, head, &map->prev);
 }
 
 union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
@@ -138,7 +118,7 @@ union perf_event *perf_mmap__read_backward(struct perf_mmap *map)
         else
                 end = head + map->mask + 1;
 
-        return perf_mmap__read(map, false, start, end, &map->prev);
+        return perf_mmap__read(map, start, end, &map->prev);
 }
 
 void perf_mmap__read_catchup(struct perf_mmap *map)
@@ -254,18 +234,18 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
         return 0;
 }
 
-static int backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)
+static int overwrite_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end)
 {
         struct perf_event_header *pheader;
         u64 evt_head = head;
         int size = mask + 1;
 
-        pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);
+        pr_debug2("overwrite_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head);
         pheader = (struct perf_event_header *)(buf + (head & mask));
         *start = head;
         while (true) {
                 if (evt_head - head >= (unsigned int)size) {
-                        pr_debug("Finished reading backward ring buffer: rewind\n");
+                        pr_debug("Finished reading overwrite ring buffer: rewind\n");
                         if (evt_head - head > (unsigned int)size)
                                 evt_head -= pheader->size;
                         *end = evt_head;
@@ -275,7 +255,7 @@ static int backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64
                 pheader = (struct perf_event_header *)(buf + (evt_head & mask));
 
                 if (pheader->size == 0) {
-                        pr_debug("Finished reading backward ring buffer: get start\n");
+                        pr_debug("Finished reading overwrite ring buffer: get start\n");
                         *end = evt_head;
                         return 0;
                 }
@@ -287,19 +267,7 @@ static int backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64
         return -1;
 }
 
-static int rb_find_range(void *data, int mask, u64 head, u64 old,
-                         u64 *start, u64 *end, bool backward)
-{
-        if (!backward) {
-                *start = old;
-                *end = head;
-                return 0;
-        }
-
-        return backward_rb_find_range(data, mask, head, start, end);
-}
-
-int perf_mmap__push(struct perf_mmap *md, bool overwrite, bool backward,
+int perf_mmap__push(struct perf_mmap *md, bool overwrite,
                     void *to, int push(void *to, void *buf, size_t size))
 {
         u64 head = perf_mmap__read_head(md);
@@ -310,19 +278,28 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite, bool backward,
         void *buf;
         int rc = 0;
 
-        if (rb_find_range(data, md->mask, head, old, &start, &end, backward))
-                return -1;
+        start = overwrite ? head : old;
+        end = overwrite ? old : head;
 
         if (start == end)
                 return 0;
 
         size = end - start;
         if (size > (unsigned long)(md->mask) + 1) {
-                WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
+                if (!overwrite) {
+                        WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n");
 
-                md->prev = head;
-                perf_mmap__consume(md, overwrite || backward);
-                return 0;
+                        md->prev = head;
+                        perf_mmap__consume(md, overwrite);
+                        return 0;
+                }
+
+                /*
+                 * Backward ring buffer is full. We still have a chance to read
+                 * most of data from it.
+                 */
+                if (overwrite_rb_find_range(data, md->mask, head, &start, &end))
+                        return -1;
         }
 
         if ((start & md->mask) + size != (end & md->mask)) {
@@ -346,7 +323,7 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite, bool backward,
         }
 
         md->prev = head;
-        perf_mmap__consume(md, overwrite || backward);
+        perf_mmap__consume(md, overwrite);
 out:
         return rc;
 }