linux-kernel - [PATCH V5 07/17] perf mmap: introduce perf_mmap__read

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Message-Id: <1516310792-208685-8-git-send-email-kan.liang@intel.com>
Date:   Thu, 18 Jan 2018 13:26:22 -0800
From:   kan.liang@...el.com
To:     acme@...nel.org, peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     wangnan0@...wei.com, jolsa@...nel.org, namhyung@...nel.org,
        ak@...ux.intel.com, yao.jin@...ux.intel.com,
        Kan Liang <kan.liang@...el.com>
Subject: [PATCH V5 07/17] perf mmap: introduce perf_mmap__read_done

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

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.liang@...el.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 */
-- 
2.5.5