linux-kernel - [PATCH 43/48] perf record: Wait for all threads being started

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Date:   Thu, 13 Sep 2018 14:54:45 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andi Kleen <andi@...stfloor.org>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>
Subject: [PATCH 43/48] perf record: Wait for all threads being started

Ensure all threads are started and ready before
we enable events. Using pthread_cond_t signaling
logic for that.

Link: http://lkml.kernel.org/n/tip-z4x5ikp8v7e3flpxoo4bv1un@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/builtin-record.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 6ad57ba6657e..fbca1d15b90d 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -102,6 +102,9 @@ struct record {
 	unsigned long long	samples;
 	struct record_thread	*threads;
 	int			threads_cnt;
+	int			threads_signal_cnt;
+	pthread_mutex_t		threads_signal_mutex;
+	pthread_cond_t		threads_signal_cond;
 	unsigned long		waking;
 };
 
@@ -1145,6 +1148,9 @@ record__threads_config(struct record *rec)
 
 	ret = record__threads_create_poll(rec);
 
+	pthread_mutex_init(&rec->threads_signal_mutex, NULL);
+	pthread_cond_init(&rec->threads_signal_cond, NULL);
+
 out:
 	if (ret)
 		record__threads_clean(rec);
@@ -1181,6 +1187,26 @@ record_thread__process(struct record *rec)
 	return NULL;
 }
 
+static void signal_main(struct record *rec)
+{
+	pthread_mutex_lock(&rec->threads_signal_mutex);
+	rec->threads_signal_cnt++;
+	pthread_cond_signal(&rec->threads_signal_cond);
+	pthread_mutex_unlock(&rec->threads_signal_mutex);
+}
+
+static void wait_for_signal(struct record *rec)
+{
+	pthread_mutex_lock(&rec->threads_signal_mutex);
+
+	while (rec->threads_signal_cnt < rec->threads_cnt) {
+		pthread_cond_wait(&rec->threads_signal_cond,
+				  &rec->threads_signal_mutex);
+	}
+
+	pthread_mutex_unlock(&rec->threads_signal_mutex);
+}
+
 static void *worker(void *arg)
 {
 	struct record_thread *th = arg;
@@ -1189,6 +1215,8 @@ static void *worker(void *arg)
 	thread        = th;
 	thread->state = RECORD_THREAD__RUNNING;
 
+	signal_main(rec);
+
 	return record_thread__process(rec);
 }
 
@@ -1197,12 +1225,17 @@ static int record__threads_start(struct record *rec)
 	struct record_thread *threads = rec->threads;
 	int i, err = 0;
 
+	rec->threads_signal_cnt = 1;
+
 	for (i = 1; !err && i < rec->threads_cnt; i++) {
 		struct record_thread *th = threads + i;
 
 		err = pthread_create(&th->pt, NULL, worker, th);
 	}
 
+	if (rec->threads_cnt > 1)
+		wait_for_signal(rec);
+
 	return err;
 }
 
-- 
2.17.1