perf daemon: Add 'list' command

Add a 'list' command to display all running sessions.  It's the default
command if no other command is specified.

Example:

  # cat ~/.perfconfig
  [daemon]
  base=/opt/perfdata

  [session-cycles]
  run = -m 10M -e cycles --overwrite --switch-output -a

  [session-sched]
  run = -m 20M -e sched:* --overwrite --switch-output -a

Start the daemon:

  # perf daemon start

List sessions:

  # perf daemon
  [771394:daemon] base: /opt/perfdata
  [771395:cycles] perf record -m 10M -e cycles --overwrite --switch-output -a
  [771396:sched] perf record -m 20M -e sched:* --overwrite --switch-output -a

List sessions with more info:

  # perf daemon -v
  [771394:daemon] base: /opt/perfdata
    output:  /opt/perfdata/output
  [771395:cycles] perf record -m 10M -e cycles --overwrite --switch-output -a
    base:    /opt/perfdata/session-cycles
    output:  /opt/perfdata/session-cycles/output
  [771396:sched] perf record -m 20M -e sched:* --overwrite --switch-output -a
    base:    /opt/perfdata/session-sched
    output:  /opt/perfdata/session-sched/output

The 'output' file is perf record output for specific session.

Note you have to stop all running perf processes manually at this point,
stop command is coming in following patches.

Committer notes:

Fixup union initialization to overcome this in multiple older systems:

  22    15.74 debian:8                      : FAIL gcc version 4.9.2 (Debian 4.9.2-10+deb8u2)

    builtin-daemon.c: In function 'send_cmd_list':
    builtin-daemon.c:1386:2: error: missing initializer for field 'csv_sep' of 'struct <anonymous>' [-Werror=missing-field-initializers]
      };
      ^
    builtin-daemon.c:641:8: note: 'csv_sep' declared here
       char csv_sep;
            ^
    cc1: all warnings being treated as errors

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210208200908.1019149-11-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-daemon.c

@@ -81,6 +81,7 @@ struct daemon {
 	const char		*config;
 	char			*config_real;
 	char			*config_base;
+	const char		*csv_sep;
 	const char		*base_user;
 	char			*base;
 	struct list_head	 sessions;
@@ -528,11 +529,78 @@ static int setup_server_socket(struct daemon *daemon)
 	return fd;
 }
 
+enum {
+	CMD_LIST   = 0,
+	CMD_MAX,
+};
+
 union cmd {
 	int cmd;
+
+	/* CMD_LIST */
+	struct {
+		int	cmd;
+		int	verbose;
+		char	csv_sep;
+	} list;
 };
 
-static int handle_server_socket(struct daemon *daemon __maybe_unused, int sock_fd)
+static int cmd_session_list(struct daemon *daemon, union cmd *cmd, FILE *out)
+{
+	char csv_sep = cmd->list.csv_sep;
+	struct daemon_session *session;
+
+	if (csv_sep) {
+		fprintf(out, "%d%c%s%c%s%c%s/%s",
+			/* pid daemon  */
+			getpid(), csv_sep, "daemon",
+			/* base */
+			csv_sep, daemon->base,
+			/* output */
+			csv_sep, daemon->base, SESSION_OUTPUT);
+
+		fprintf(out, "\n");
+	} else {
+		fprintf(out, "[%d:daemon] base: %s\n", getpid(), daemon->base);
+		if (cmd->list.verbose) {
+			fprintf(out, "  output:  %s/%s\n",
+				daemon->base, SESSION_OUTPUT);
+		}
+	}
+
+	list_for_each_entry(session, &daemon->sessions, list) {
+		if (csv_sep) {
+			fprintf(out, "%d%c%s%c%s",
+				/* pid */
+				session->pid,
+				/* name */
+				csv_sep, session->name,
+				/* base */
+				csv_sep, session->run);
+
+			fprintf(out, "%c%s%c%s/%s",
+				/* session dir */
+				csv_sep, session->base,
+				/* session output */
+				csv_sep, session->base, SESSION_OUTPUT);
+
+			fprintf(out, "\n");
+		} else {
+			fprintf(out, "[%d:%s] perf record %s\n",
+				session->pid, session->name, session->run);
+			if (!cmd->list.verbose)
+				continue;
+			fprintf(out, "  base:    %s\n",
+				session->base);
+			fprintf(out, "  output:  %s/%s\n",
+				session->base, SESSION_OUTPUT);
+		}
+	}
+
+	return 0;
+}
+
+static int handle_server_socket(struct daemon *daemon, int sock_fd)
 {
 	int ret = -1, fd;
 	FILE *out = NULL;
@@ -556,6 +624,9 @@ static int handle_server_socket(struct daemon *daemon __maybe_unused, int sock_f
 	}
 
 	switch (cmd.cmd) {
+	case CMD_LIST:
+		ret = cmd_session_list(daemon, &cmd, out);
+		break;
 	default:
 		break;
 	}
@@ -968,7 +1039,6 @@ static int __cmd_start(struct daemon *daemon, struct option parent_options[],
 	return err;
 }
 
-__maybe_unused
 static int send_cmd(struct daemon *daemon, union cmd *cmd)
 {
 	int ret = -1, fd;
@@ -1012,6 +1082,16 @@ static int send_cmd(struct daemon *daemon, union cmd *cmd)
 	return ret;
 }
 
+static int send_cmd_list(struct daemon *daemon)
+{
+	union cmd cmd = { .cmd = CMD_LIST, };
+
+	cmd.list.verbose = verbose;
+	cmd.list.csv_sep = daemon->csv_sep ? *daemon->csv_sep : 0;
+
+	return send_cmd(daemon, &cmd);
+}
+
 int cmd_daemon(int argc, const char **argv)
 {
 	struct option daemon_options[] = {
@@ -1020,6 +1100,8 @@ int cmd_daemon(int argc, const char **argv)
 			"config file", "config file path"),
 		OPT_STRING(0, "base", &__daemon.base_user,
 			"directory", "base directory"),
+		OPT_STRING_OPTARG('x', "field-separator", &__daemon.csv_sep,
+			"field separator", "print counts with custom separator", ","),
 		OPT_END()
 	};
 
@@ -1042,5 +1124,5 @@ int cmd_daemon(int argc, const char **argv)
 		return -1;
 	}
 
-	return -1;
+	return send_cmd_list(&__daemon);
 }