[PATCH v2 03/13] perf tools: Add API to pause a evlist

[Wang Nan]

perf_evlist__toggle_paused() is introduced to pause/resume events
in an evlist. Utilize PERF_EVENT_IOC_PAUSE_OUTPUT ioctl. Following
commits use perf_evlist__toggle_paused() to ensure overwrite
ring buffer is paused before reading.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/evlist.c | 22 ++++++++++++++++++++++
 tools/perf/util/evlist.h |  1 +
 2 files changed, 23 insertions(+)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 1a370db..f4bb8be 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -679,6 +679,28 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist,
 	return NULL;
 }
 
+int perf_evlist__toggle_paused(struct perf_evlist *evlist, bool pause)
+{
+	int i;
+
+	for (i = 0; i < evlist->nr_mmaps; i++) {
+		int fd = evlist->mmap[i].fd;
+		int err;
+
+		if (fd < 0)
+			continue;
+		err = ioctl(fd, PERF_EVENT_IOC_PAUSE_OUTPUT,
+			    pause ? 1 : 0);
+		if (err) {
+			err = (errno == 0 ? -EINVAL : -errno);
+			pr_err("Unable to pause output on %d: %s\n",
+			       fd, strerror(-err));
+			return err;
+		}
+	}
+	return 0;
+}
+
 /* When check_messup is true, 'end' must points to a good entry */
 static union perf_event *
 perf_mmap__read(struct perf_mmap *md, bool check_messup, u64 start,
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index 0d165b1..13234dc 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -136,6 +136,7 @@ void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx);
 
 void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx);
 
+int perf_evlist__toggle_paused(struct perf_evlist *evlist, bool pause);
 int perf_evlist__open(struct perf_evlist *evlist);
 void perf_evlist__close(struct perf_evlist *evlist);
 
-- 
1.8.3.4