1 files changed, 17 insertions, 0 deletions
diff --git a/tools/perf/lib/mmap.c b/tools/perf/lib/mmap.c
index fdbc6c550dea..97297cba44e3 100644
--- a/tools/perf/lib/mmap.c
+++ b/tools/perf/lib/mmap.c
@@ -175,3 +175,20 @@ int perf_mmap__read_init(struct perf_mmap *map)
 
 	return __perf_mmap__read_init(map);
 }
+
+/*
+ * Mandatory for overwrite mode
+ * The direction of overwrite mode is backward.
+ * The last perf_mmap__read() will set tail to map->core.prev.
+ * Need to correct the map->core.prev to head which is the end of next read.
+ */
+void perf_mmap__read_done(struct perf_mmap *map)
+{
+	/*
+	 * Check if event was unmapped due to a POLLHUP/POLLERR.
+	 */
+	if (!refcount_read(&map->refcnt))
+		return;
+
+	map->prev = perf_mmap__read_head(map);
+}