[PATCH 5/6] perf record: Add 'snapshot' control command

[Adrian Hunter <adrian.hunter@intel.com>]

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 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>
---
 tools/perf/Documentation/perf-record.txt |  8 ++++----
 tools/perf/builtin-record.c              | 24 +++++++++++++++++-------
 tools/perf/builtin-stat.c                |  1 +
 tools/perf/util/evlist.c                 | 11 +++++++++--
 tools/perf/util/evlist.h                 |  5 ++++-
 5 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 74fa3e905bf1..0c028d48ebd0 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -631,10 +631,10 @@ endif::HAVE_LIBPFM[]
 --control=fd:ctl-fd[,ack-fd]::
 ctl-fifo / ack-fifo are opened and used as ctl-fd / ack-fd as follows.
 Listen on ctl-fd descriptor for command to control measurement ('enable': enable events,
-'disable': disable events). Measurements can be started with events disabled using
---delay=-1 option. Optionally send control command completion ('ack\n') to ack-fd descriptor
-to synchronize with the controlling process. Example of bash shell script to enable and
-disable events during measurements:
+'disable': disable events, 'snapshot': AUX area tracing snapshot). Measurements can be
+started with events disabled using --delay=-1 option. Optionally send control command
+completion ('ack\n') to ack-fd descriptor to synchronize with the controlling process.
+Example of bash shell script to enable and disable events during measurements:
 
  #!/bin/bash
 
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index af7238b1356f..77d86a3a8553 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 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);
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 0d4495bace13..3536299496a8 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -578,6 +578,7 @@ static void process_evlist(struct evlist *evlist, unsigned int interval)
 				process_interval();
 			pr_info(EVLIST_DISABLED_MSG);
 			break;
+		case EVLIST_CTL_CMD_SNAPSHOT:
 		case EVLIST_CTL_CMD_ACK:
 		case EVLIST_CTL_CMD_UNSUPPORTED:
 		default:
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index cb61c223927f..bd88521a01a5 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1881,13 +1881,17 @@ static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd,
 		} else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG,
 				    (sizeof(EVLIST_CTL_CMD_DISABLE_TAG)-1))) {
 			*cmd = EVLIST_CTL_CMD_DISABLE;
+		} else if (!strncmp(cmd_data, EVLIST_CTL_CMD_SNAPSHOT_TAG,
+				    (sizeof(EVLIST_CTL_CMD_SNAPSHOT_TAG)-1))) {
+			*cmd = EVLIST_CTL_CMD_SNAPSHOT;
+			pr_debug("is snapshot\n");
 		}
 	}
 
 	return bytes_read ? (int)bytes_read : err;
 }
 
-static int evlist__ctlfd_ack(struct evlist *evlist)
+int evlist__ctlfd_ack(struct evlist *evlist)
 {
 	int err;
 
@@ -1923,13 +1927,16 @@ int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd)
 			case EVLIST_CTL_CMD_DISABLE:
 				evlist__disable(evlist);
 				break;
+			case EVLIST_CTL_CMD_SNAPSHOT:
+				break;
 			case EVLIST_CTL_CMD_ACK:
 			case EVLIST_CTL_CMD_UNSUPPORTED:
 			default:
 				pr_debug("ctlfd: unsupported %d\n", *cmd);
 				break;
 			}
-			if (!(*cmd == EVLIST_CTL_CMD_ACK || *cmd == EVLIST_CTL_CMD_UNSUPPORTED))
+			if (!(*cmd == EVLIST_CTL_CMD_ACK || *cmd == EVLIST_CTL_CMD_UNSUPPORTED ||
+			      *cmd == EVLIST_CTL_CMD_SNAPSHOT))
 				evlist__ctlfd_ack(evlist);
 		}
 	}
diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h
index a5678eb5ee60..91d1da6e1fe3 100644
--- a/tools/perf/util/evlist.h
+++ b/tools/perf/util/evlist.h
@@ -363,6 +363,7 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evlist,
 #define EVLIST_CTL_CMD_ENABLE_TAG  "enable"
 #define EVLIST_CTL_CMD_DISABLE_TAG "disable"
 #define EVLIST_CTL_CMD_ACK_TAG     "ack\n"
+#define EVLIST_CTL_CMD_SNAPSHOT_TAG "snapshot"
 
 #define EVLIST_CTL_CMD_MAX_LEN 64
 
@@ -370,7 +371,8 @@ enum evlist_ctl_cmd {
 	EVLIST_CTL_CMD_UNSUPPORTED = 0,
 	EVLIST_CTL_CMD_ENABLE,
 	EVLIST_CTL_CMD_DISABLE,
-	EVLIST_CTL_CMD_ACK
+	EVLIST_CTL_CMD_ACK,
+	EVLIST_CTL_CMD_SNAPSHOT,
 };
 
 int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack, bool *ctl_fd_close);
@@ -378,6 +380,7 @@ int evlist__initialize_ctlfd(struct evlist *evlist, int ctl_fd, int ctl_fd_ack);
 int evlist__finalize_ctlfd(struct evlist *evlist);
 bool evlist__ctlfd_initialized(struct evlist *evlist);
 int evlist__ctlfd_process(struct evlist *evlist, enum evlist_ctl_cmd *cmd);
+int evlist__ctlfd_ack(struct evlist *evlist);
 
 #define EVLIST_ENABLED_MSG "Events enabled\n"
 #define EVLIST_DISABLED_MSG "Events disabled\n"
-- 
2.17.1