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: stable@vger.kernel.org
Cc: John Kacur <jkacur@redhat.com>
Cc: Luis Goncalves <lgoncalv@redhat.com>
Cc: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/20250116144931.649593-3-tglozar@redhat.com
Fixes: 1eeb6328e8b3 ("rtla/timerlat: Add timerlat hist mode")
Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/tools/tracing/rtla/src/timerlat_hist.c b/tools/tracing/rtla/src/timerlat_hist.c
index 8b66387e5f35c7d357bd10c3a93d38d6132d2587..f1edf1c8a7b071f081a92b9f305a5cd1f6c91c65 100644 (file)
--- a/tools/tracing/rtla/src/timerlat_hist.c
+++ b/tools/tracing/rtla/src/timerlat_hist.c
@@ -1131,9 +1131,12 @@ out_err:
 }
 
 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)