[PATCH v1 4/8] perf stat: implement resume and pause control commands handling

[Alexey Budankov]

Implement handle_events() function to handle multiple events
coming from different sources during the measurement in various
modes. Events can come from workload being monitored, signals can
asynchronously arrive, control file descriptors can deliver resume
and pause commands from external processes.

Signed-off-by: Alexey Budankov <alexey.budankov@xxxxxxxxxxxxxxx>
---
 tools/perf/builtin-stat.c | 110 +++++++++++++++++++++++++-------------
 1 file changed, 74 insertions(+), 36 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 0a1b79fd3f48..58a1b2ff90f7 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -373,6 +373,16 @@ static void process_interval(void)
 	print_counters(&rs, 0, NULL);
 }
 
+static bool print_interval_and_stop(struct perf_stat_config *config, int *times)
+{
+	if (config->interval) {
+		process_interval();
+		if (interval_count && !(--(*times)))
+			return true;
+	}
+	return false;
+}
+
 static void enable_counters(void)
 {
 	if (stat_config.initial_delay < 0) {
@@ -448,6 +458,66 @@ static bool is_target_alive(struct target *_target,
 	return false;
 }
 
+static int handle_events(pid_t pid, struct perf_stat_config *config)
+{
+	pid_t child = 0;
+	bool res, stop = false;
+	int sleep_time, time_to_sleep, status = 0, times = config->times;
+	enum evlist_ctl_cmd cmd = CTL_CMD_UNSUPPORTED;
+	struct timespec time_start, time_stop, time_diff;
+
+	if (config->interval)
+		sleep_time = config->interval;
+	else if (config->timeout)
+		sleep_time = config->timeout;
+	else
+		sleep_time = 1000;
+
+	time_to_sleep = sleep_time;
+
+	do {
+		if (pid != -1)
+			child = wait4(pid, &status, WNOHANG, &(config->ru_data));
+		if (child || stop || done)
+			break;
+		clock_gettime(CLOCK_MONOTONIC, &time_start);
+		if (evlist__poll(evsel_list, time_to_sleep) > 0) { /* fd revent */
+			if (perf_evlist__ctlfd_process(evsel_list, &cmd) > 0) {
+				switch (cmd) {
+				case CTL_CMD_RESUME:
+					pr_info(PERF_EVLIST__RESUMED_MSG);
+					stop = print_interval_and_stop(config, &times);
+					break;
+				case CTL_CMD_PAUSE:
+					stop = print_interval_and_stop(config, &times);
+					pr_info(PERF_EVLIST__PAUSED_MSG);
+					break;
+				case CTL_CMD_ACK:
+				case CTL_CMD_UNSUPPORTED:
+				default:
+					break;
+				}
+			}
+			clock_gettime(CLOCK_MONOTONIC, &time_stop);
+			diff_timespec(&time_diff, &time_stop, &time_start);
+			time_to_sleep -= time_diff.tv_sec * MSEC_PER_SEC +
+					 time_diff.tv_nsec / NSEC_PER_MSEC;
+		} else { /* poll timeout or EINTR */
+			if (pid == -1)
+				stop = !is_target_alive(&target, evsel_list->core.threads);
+			if (config->timeout) {
+				stop = !stop ? true : stop;
+			} else {
+				res = print_interval_and_stop(config, &times);
+				stop = !stop ? res : stop;
+			}
+			time_to_sleep = sleep_time;
+		}
+	} while (1);
+
+	return status;
+}
+
 enum counter_recovery {
 	COUNTER_SKIP,
 	COUNTER_RETRY,
@@ -507,12 +577,10 @@ static enum counter_recovery stat_handle_error(struct evsel *counter)
 static int __run_perf_stat(int argc, const char **argv, int run_idx)
 {
 	int interval = stat_config.interval;
-	int times = stat_config.times;
 	int timeout = stat_config.timeout;
 	char msg[BUFSIZ];
 	unsigned long long t0, t1;
 	struct evsel *counter;
-	struct timespec ts;
 	size_t l;
 	int status = 0;
 	const bool forks = (argc > 0);
@@ -521,17 +589,6 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 	int i, cpu;
 	bool second_pass = false;
 
-	if (interval) {
-		ts.tv_sec  = interval / USEC_PER_MSEC;
-		ts.tv_nsec = (interval % USEC_PER_MSEC) * NSEC_PER_MSEC;
-	} else if (timeout) {
-		ts.tv_sec  = timeout / USEC_PER_MSEC;
-		ts.tv_nsec = (timeout % USEC_PER_MSEC) * NSEC_PER_MSEC;
-	} else {
-		ts.tv_sec  = 1;
-		ts.tv_nsec = 0;
-	}
-
 	if (forks) {
 		if (perf_evlist__prepare_workload(evsel_list, &target, argv, is_pipe,
 						  workload_exec_failed_signal) < 0) {
@@ -688,18 +745,10 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 		perf_evlist__start_workload(evsel_list);
 		enable_counters();
 
-		if (interval || timeout) {
-			while (!waitpid(child_pid, &status, WNOHANG)) {
-				nanosleep(&ts, NULL);
-				if (timeout)
-					break;
-				process_interval();
-				if (interval_count && !(--times))
-					break;
-			}
-		}
-		if (child_pid != -1)
+		if (stat_config.ctl_fd == -1 && !interval && !timeout)
 			wait4(child_pid, &status, 0, &stat_config.ru_data);
+		else
+			status = handle_events(child_pid, &stat_config);
 
 		if (workload_exec_errno) {
 			const char *emsg = str_error_r(workload_exec_errno, msg, sizeof(msg));
@@ -711,18 +760,7 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
 			psignal(WTERMSIG(status), argv[0]);
 	} else {
 		enable_counters();
-		while (!done) {
-			nanosleep(&ts, NULL);
-			if (!is_target_alive(&target, evsel_list->core.threads))
-				break;
-			if (timeout)
-				break;
-			if (interval) {
-				process_interval();
-				if (interval_count && !(--times))
-					break;
-			}
-		}
+		handle_events(-1, &stat_config);
 	}
 
 	disable_counters();
-- 
2.24.1