@@ -766,6 +766,56 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx)
return perf_mmap__read(md, evlist->overwrite, old, head, &md->prev);
}
+union perf_event *
+perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx)
+{
+ struct perf_mmap *md = &evlist->mmap[idx];
+ u64 head, end;
+ u64 start = md->prev;
+
+ /*
+ * Check if event was unmapped due to a POLLHUP/POLLERR.
+ */
+ if (!atomic_read(&md->refcnt))
+ return NULL;
+
+ head = perf_mmap__read_head(md);
+ if (!head)
+ return NULL;
+
+ /*
+ * 'head' pointer starts from 0. Kernel minus sizeof(record) form
+ * it each time when kernel writes to it, so in fact 'head' is
+ * negative. 'end' pointer is made manually by adding the size of
+ * the ring buffer to 'head' pointer, means the validate data can
+ * read is the whole ring buffer. If 'end' is positive, the ring
+ * buffer has not fully filled, so we must adjust 'end' to 0.
+ *
+ * However, since both 'head' and 'end' is unsigned, we can't
+ * simply compare 'end' against 0. Here we compare '-head' and
+ * the size of the ring buffer, where -head is the number of bytes
+ * kernel write to the ring buffer.
+ */
+ if (-head < (u64)(md->mask + 1))
+ end = 0;
+ else
+ end = head + md->mask + 1;
+
+ return perf_mmap__read(md, false, start, end, &md->prev);
+}
+
+void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx)
+{
+ struct perf_mmap *md = &evlist->mmap[idx];
+ u64 head;
+
+ if (!atomic_read(&md->refcnt))
+ return;
+
+ head = perf_mmap__read_head(md);
+ md->prev = head;
+}
+
static bool perf_mmap__empty(struct perf_mmap *md)
{
return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base;
@@ -129,6 +129,10 @@ struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id);
union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx);
+union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist,
+ int idx);
+void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx);
+
void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx);
int perf_evlist__open(struct perf_evlist *evlist);