[PATCH v1 10/14] perf intel-tpebs: Add mutex for tpebs_results

[Ian Rogers]

Ensure sample reader isn't racing with events being added/removed.

Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 tools/perf/util/intel-tpebs.c | 51 ++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/intel-tpebs.c b/tools/perf/util/intel-tpebs.c
index 486218757872..05e1a0a296c5 100644
--- a/tools/perf/util/intel-tpebs.c
+++ b/tools/perf/util/intel-tpebs.c
@@ -16,6 +16,7 @@
 #include "debug.h"
 #include "evlist.h"
 #include "evsel.h"
+#include "mutex.h"
 #include "session.h"
 #include "tool.h"
 #include "cpumap.h"
@@ -31,6 +32,7 @@ bool tpebs_recording;
 static LIST_HEAD(tpebs_results);
 static pthread_t tpebs_reader_thread;
 static struct child_process tpebs_cmd;
+static struct mutex tpebs_mtx;
 
 struct tpebs_retire_lat {
 	struct list_head nd;
@@ -50,6 +52,19 @@ struct tpebs_retire_lat {
 
 static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel);
 
+static void tpebs_mtx_init(void)
+{
+	mutex_init(&tpebs_mtx);
+}
+
+static struct mutex *tpebs_mtx_get(void)
+{
+	static pthread_once_t tpebs_mtx_once = PTHREAD_ONCE_INIT;
+
+	pthread_once(&tpebs_mtx_once, tpebs_mtx_init);
+	return &tpebs_mtx;
+}
+
 static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[], int ack_fd[])
 {
 	const char **record_argv;
@@ -58,13 +73,15 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[],
 	char cpumap_buf[50];
 	struct tpebs_retire_lat *t;
 
+	mutex_lock(tpebs_mtx_get());
 	list_for_each_entry(t, &tpebs_results, nd)
 		tpebs_event_size++;
 
 	record_argv = malloc((10 + 2 * tpebs_event_size) * sizeof(*record_argv));
-	if (!record_argv)
+	if (!record_argv) {
+		mutex_unlock(tpebs_mtx_get());
 		return -ENOMEM;
-
+	}
 	record_argv[i++] = "perf";
 	record_argv[i++] = "record";
 	record_argv[i++] = "-W";
@@ -100,6 +117,7 @@ static int evsel__tpebs_start_perf_record(struct evsel *evsel, int control_fd[],
 	list_for_each_entry(t, &tpebs_results, nd)
 		t->started = true;
 
+	mutex_unlock(tpebs_mtx_get());
 	return ret;
 }
 
@@ -111,9 +129,12 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused,
 {
 	struct tpebs_retire_lat *t;
 
+	mutex_lock(tpebs_mtx_get());
 	t = tpebs_retire_lat__find(evsel);
-	if (!t)
+	if (!t) {
+		mutex_unlock(tpebs_mtx_get());
 		return -EINVAL;
+	}
 	/*
 	 * Need to handle per core results? We are assuming average retire
 	 * latency value will be used. Save the number of samples and the sum of
@@ -122,6 +143,7 @@ static int process_sample_event(const struct perf_tool *tool __maybe_unused,
 	t->count += 1;
 	t->sum += sample->retire_lat;
 	t->val = (double) t->sum / t->count;
+	mutex_unlock(tpebs_mtx_get());
 	return 0;
 }
 
@@ -228,7 +250,6 @@ static struct tpebs_retire_lat *tpebs_retire_lat__new(struct evsel *evsel)
 		return NULL;
 	}
 	result->evsel = evsel;
-	list_add_tail(&result->nd, &tpebs_results);
 	return result;
 }
 
@@ -276,16 +297,22 @@ static struct tpebs_retire_lat *tpebs_retire_lat__find(struct evsel *evsel)
 static int evsel__tpebs_prepare(struct evsel *evsel)
 {
 	struct evsel *pos;
-	struct tpebs_retire_lat *tpebs_event = tpebs_retire_lat__find(evsel);
+	struct tpebs_retire_lat *tpebs_event;
 
+	mutex_lock(tpebs_mtx_get());
+	tpebs_event = tpebs_retire_lat__find(evsel);
 	if (tpebs_event) {
 		/* evsel, or an identically named one, was already prepared. */
+		mutex_unlock(tpebs_mtx_get());
 		return 0;
 	}
 	tpebs_event = tpebs_retire_lat__new(evsel);
 	if (!tpebs_event)
 		return -ENOMEM;
 
+	list_add_tail(&tpebs_event->nd, &tpebs_results);
+	mutex_unlock(tpebs_mtx_get());
+
 	/*
 	 * Eagerly prepare all other evsels on the list to try to ensure that by
 	 * open they are all known.
@@ -311,6 +338,7 @@ static int evsel__tpebs_prepare(struct evsel *evsel)
 int evsel__tpebs_open(struct evsel *evsel)
 {
 	int ret;
+	bool tpebs_empty;
 
 	/* We should only run tpebs_start when tpebs_recording is enabled. */
 	if (!tpebs_recording)
@@ -330,7 +358,10 @@ int evsel__tpebs_open(struct evsel *evsel)
 	if (ret)
 		return ret;
 
-	if (!list_empty(&tpebs_results)) {
+	mutex_lock(tpebs_mtx_get());
+	tpebs_empty = list_empty(&tpebs_results);
+	mutex_unlock(tpebs_mtx_get());
+	if (!tpebs_empty) {
 		struct pollfd pollfd = { .events = POLLIN, };
 		int control_fd[2], ack_fd[2], len;
 		char ack_buf[8];
@@ -430,8 +461,10 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread)
 	 */
 	tpebs_stop();
 
+	mutex_lock(tpebs_mtx_get());
 	t = tpebs_retire_lat__find(evsel);
 	val = rint(t->val);
+	mutex_unlock(tpebs_mtx_get());
 
 	if (old_count) {
 		count->val = old_count->val + val;
@@ -454,9 +487,13 @@ int evsel__tpebs_read(struct evsel *evsel, int cpu_map_idx, int thread)
  */
 void evsel__tpebs_close(struct evsel *evsel)
 {
-	struct tpebs_retire_lat *t = tpebs_retire_lat__find(evsel);
+	struct tpebs_retire_lat *t;
 
+	mutex_lock(tpebs_mtx_get());
+	t = tpebs_retire_lat__find(evsel);
+	list_del_init(&t->nd);
 	tpebs_retire_lat__delete(t);
+	mutex_unlock(tpebs_mtx_get());
 
 	if (list_empty(&tpebs_results))
 		tpebs_stop();
-- 
2.49.0.395.g12beb8f557-goog