libperf: Adopt perf_mmap__read_done() from tools/perf
Move perf_mmap__read_init() from tools/perf to libperf and export it in
the perf/mmap.h header.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191007125344.14268-12-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/lib/mmap.c b/tools/perf/lib/mmap.c
index fdbc6c5..97297cb 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);
+}