[PATCH v8 04/22] perf record: Stop threads in the end of trace streaming

[Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>]

Signal thread to terminate by closing write fd of msg pipe.
Receive THREAD_MSG__READY message as the confirmation of the
thread's termination. Stop threads created for parallel trace
streaming prior their stats processing.

Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Alexey Bayduraev <alexey.v.bayduraev@linux.intel.com>
---
 tools/perf/builtin-record.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 3935c0fabe01..82a21da2af16 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -112,6 +112,16 @@ struct thread_data {
 
 static __thread struct thread_data *thread;
 
+enum thread_msg {
+	THREAD_MSG__UNDEFINED = 0,
+	THREAD_MSG__READY,
+	THREAD_MSG__MAX,
+};
+
+static const char *thread_msg_tags[THREAD_MSG__MAX] = {
+	"UNDEFINED", "READY"
+};
+
 struct record {
 	struct perf_tool	tool;
 	struct record_opts	opts;
@@ -1857,6 +1867,23 @@ static void record__uniquify_name(struct record *rec)
 	}
 }
 
+static int record__terminate_thread(struct thread_data *thread_data)
+{
+	int res;
+	enum thread_msg ack = THREAD_MSG__UNDEFINED;
+	pid_t tid = thread_data->tid;
+
+	close(thread_data->pipes.msg[1]);
+	res = read(thread_data->pipes.ack[0], &ack, sizeof(ack));
+	if (res != -1)
+		pr_debug2("threads[%d]: sent %s\n", tid, thread_msg_tags[ack]);
+	else
+		pr_err("threads[%d]: failed to recv msg=%s from tid=%d\n",
+		       thread->tid, thread_msg_tags[ack], tid);
+
+	return 0;
+}
+
 static int record__start_threads(struct record *rec)
 {
 	struct thread_data *thread_data = rec->thread_data;
@@ -1873,6 +1900,9 @@ static int record__stop_threads(struct record *rec, unsigned long *waking)
 	int t;
 	struct thread_data *thread_data = rec->thread_data;
 
+	for (t = 1; t < rec->nr_threads; t++)
+		record__terminate_thread(&thread_data[t]);
+
 	for (t = 0; t < rec->nr_threads; t++) {
 		rec->samples += thread_data[t].samples;
 		*waking += thread_data[t].waking;
-- 
2.19.0