perf record: Add 'snapshot' control command

Add 'snapshot' control command to create an AUX area tracing snapshot
the same as if sending SIGUSR2. The advantage of the FIFO is that access
is governed by access to the FIFO.

Example:

  $ mkfifo perf.control
  $ mkfifo perf.ack
  $ cat perf.ack &
  [1] 15235
  $ sudo ~/bin/perf record --control fifo:perf.control,perf.ack -S -e intel_pt//u -- sleep 60 &
  [2] 15243
  $ ps -e | grep perf
   15244 pts/1    00:00:00 perf
  $ kill -USR2 15244
  bash: kill: (15244) - Operation not permitted
  $ echo snapshot > perf.control
  ack
  $

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20200901093758.32293-6-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 17 insertions, 7 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index c83aec4940de..d0f9f8107f47 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1593,6 +1593,16 @@ static int record__init_clock(struct record *rec)
 	return 0;
 }
 
+static void hit_auxtrace_snapshot_trigger(struct record *rec)
+{
+	if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
+		trigger_hit(&auxtrace_snapshot_trigger);
+		auxtrace_record__snapshot_started = 1;
+		if (auxtrace_record__snapshot_start(rec->itr))
+			trigger_error(&auxtrace_snapshot_trigger);
+	}
+}
+
 static int __cmd_record(struct record *rec, int argc, const char **argv)
 {
 	int err;
@@ -1937,6 +1947,10 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
 			case EVLIST_CTL_CMD_DISABLE:
 				pr_info(EVLIST_DISABLED_MSG);
 				break;
+			case EVLIST_CTL_CMD_SNAPSHOT:
+				hit_auxtrace_snapshot_trigger(rec);
+				evlist__ctlfd_ack(rec->evlist);
+				break;
 			case EVLIST_CTL_CMD_ACK:
 			case EVLIST_CTL_CMD_UNSUPPORTED:
 			default:
@@ -2589,7 +2603,8 @@ static struct option __record_options[] = {
 		parse_libpfm_events_option),
 #endif
 	OPT_CALLBACK(0, "control", &record.opts, "fd:ctl-fd[,ack-fd] or fifo:ctl-fifo[,ack-fifo]",
-		     "Listen on ctl-fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events).\n"
+		     "Listen on ctl-fd descriptor for command to control measurement ('enable': enable events, 'disable': disable events,\n"
+		     "\t\t\t  'snapshot': AUX area tracing snapshot).\n"
 		     "\t\t\t  Optionally send control command completion ('ack\\n') to ack-fd descriptor.\n"
 		     "\t\t\t  Alternatively, ctl-fifo / ack-fifo will be opened and used as ctl-fd / ack-fd.",
 		      parse_control_option),
@@ -2842,12 +2857,7 @@ static void snapshot_sig_handler(int sig __maybe_unused)
 {
 	struct record *rec = &record;
 
-	if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
-		trigger_hit(&auxtrace_snapshot_trigger);
-		auxtrace_record__snapshot_started = 1;
-		if (auxtrace_record__snapshot_start(record.itr))
-			trigger_error(&auxtrace_snapshot_trigger);
-	}
+	hit_auxtrace_snapshot_trigger(rec);
 
 	if (switch_output_signal(rec))
 		trigger_hit(&switch_output_trigger);