Commit-ID:  f4075778f7c9f743109e59311b1bdd60f914804e
Gitweb:     https://git.kernel.org/tip/f4075778f7c9f743109e59311b1bdd60f914804e
Author:     Kan Liang <kan.li...@intel.com>
AuthorDate: Thu, 18 Jan 2018 13:26:22 -0800
Committer:  Arnaldo Carvalho de Melo <a...@redhat.com>
CommitDate: Tue, 6 Feb 2018 10:11:50 -0300

perf mmap: Introduce perf_mmap__read_done()

The direction of overwrite mode is backward. The last perf_mmap__read()
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.li...@intel.com>
Acked-by: Jiri Olsa <jo...@kernel.org>
Cc: Andi Kleen <a...@linux.intel.com>
Cc: Jin Yao <yao....@linux.intel.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Wang Nan <wangn...@huawei.com>
Link: 
http://lkml.kernel.org/r/1516310792-208685-8-git-send-email-kan.li...@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.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 125bfda..4f59eae 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -338,3 +338,14 @@ 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 perf_mmap__read() 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 9ab2b48..95549d4 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 *md, bool overwrite,
                         u64 *startp, u64 *endp);
+void perf_mmap__read_done(struct perf_mmap *map);
 #endif /*__PERF_MMAP_H */

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