[PATCH V3 04/12] perf mmap: introduce perf_mmap__read_done

[kan.liang@intel.com]

From: Kan Liang <kan.liang@intel.com>

The direction of overwrite mode is backward. The last mmap__read_event
will set tail to map->prev. Need to correct the map->prev to head which
is the end of next read.

It will be used later.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---
 tools/perf/util/mmap.c | 11 +++++++++++
 tools/perf/util/mmap.h |  1 +
 2 files changed, 12 insertions(+)

diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index a844a2f..4aaeb64 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -343,3 +343,14 @@ int perf_mmap__push(struct perf_mmap *md, bool overwrite,
 out:
 	return rc;
 }
+
+/*
+ * Mandatory for overwrite mode
+ * The direction of overwrite mode is backward.
+ * The last mmap__read_event will set tail to map->prev.
+ * Need to correct the map->prev to head which is the end of next read.
+ */
+void perf_mmap__read_done(struct perf_mmap *map)
+{
+	map->prev = perf_mmap__read_head(map);
+}
diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
index abe9b9f..2df27c1 100644
--- a/tools/perf/util/mmap.h
+++ b/tools/perf/util/mmap.h
@@ -96,4 +96,5 @@ size_t perf_mmap__mmap_len(struct perf_mmap *map);
 
 int perf_mmap__read_init(struct perf_mmap *map, bool overwrite,
 			 u64 *start, u64 *end);
+void perf_mmap__read_done(struct perf_mmap *map);
 #endif /*__PERF_MMAP_H */
-- 
2.5.5