rtla/timerlat_hist: Stop timerlat tracer on signal

Currently, when either SIGINT from the user or SIGALRM from the duration
timer is caught by rtla-timerlat, stop_tracing is set to break out of
the main loop. This is not sufficient for cases where the timerlat
tracer is producing more data than rtla can consume, since in that case,
rtla is looping indefinitely inside tracefs_iterate_raw_events, never
reaches the check of stop_tracing and hangs.

In addition to setting stop_tracing, also stop the timerlat tracer on
received signal (SIGINT or SIGALRM). This will stop new samples so that
the existing samples may be processed and tracefs_iterate_raw_events
eventually exits.

Cc: [email protected]
Cc: John Kacur <[email protected]>
Cc: Luis Goncalves <[email protected]>
Cc: Gabriele Monaco <[email protected]>
Link: https://lore.kernel.org/[email protected]
Fixes: 1eeb632 ("rtla/timerlat: Add timerlat hist mode")
Signed-off-by: Tomas Glozar <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: lenticularis39

tools/tracing/rtla/src/timerlat_hist.c

@@ -1131,9 +1131,12 @@ static struct osnoise_tool
 }
 
 static int stop_tracing;
+static struct trace_instance *hist_inst = NULL;
 static void stop_hist(int sig)
 {
 	stop_tracing = 1;
+	if (hist_inst)
+		trace_instance_stop(hist_inst);
 }
 
 /*
@@ -1180,6 +1183,12 @@ int timerlat_hist_main(int argc, char *argv[])
 	}
 
 	trace = &tool->trace;
+	/*
+	 * Save trace instance into global variable so that SIGINT can stop
+	 * the timerlat tracer.
+	 * Otherwise, rtla could loop indefinitely when overloaded.
+	 */
+	hist_inst = trace;
 
 	retval = enable_timerlat(trace);
 	if (retval) {
@@ -1348,7 +1357,7 @@ int timerlat_hist_main(int argc, char *argv[])
 
 	return_value = 0;
 
-	if (trace_is_off(&tool->trace, &record->trace)) {
+	if (trace_is_off(&tool->trace, &record->trace) && !stop_tracing) {
 		printf("rtla timerlat hit stop tracing\n");
 
 		if (!params->no_aa)