perf tools: Add FIFO file names as alternative options to --control

Enable the --control option to accept file names as an alternative to
file descriptors.

Example:

  $ mkfifo perf.control
  $ mkfifo perf.ack
  $ cat perf.ack &
  [1] 6808
  $ perf record --control fifo:perf.control,perf.ack -- sleep 300 &
  [2] 6810
  $ echo disable > perf.control
  $ Events disabled
  ack

  $ echo enable > perf.control
  $ Events enabled
  ack

  $ echo disable > perf.control
  $ Events disabled
  ack

  $ kill %2
  [ perf record: Woken up 4 times to write data ]
  $ [ perf record: Captured and wrote 0.018 MB perf.data (7 samples) ]

  [1]-  Done                    cat perf.ack
  [2]+  Terminated              perf record --control fifo:perf.control,perf.ack -- sleep 300
  $

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/20200902105707.11491-1-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-record.txt

@@ -631,7 +631,9 @@ option. The -e option and this one can be mixed and matched.  Events
 can be grouped using the {} notation.
 endif::HAVE_LIBPFM[]
 
+--control=fifo:ctl-fifo[,ack-fifo]::
 --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

tools/perf/Documentation/perf-stat.txt

@@ -180,7 +180,9 @@ with it.  --append may be used here.  Examples:
      3>results  perf stat --log-fd 3          -- $cmd
      3>>results perf stat --log-fd 3 --append -- $cmd
 
+--control=fifo:ctl-fifo[,ack-fifo]::
 --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

tools/perf/builtin-record.c

@@ -2236,7 +2236,17 @@ static int parse_control_option(const struct option *opt,
 {
 	struct record_opts *opts = opt->value;
 
-	return evlist__parse_control(str, &opts->ctl_fd, &opts->ctl_fd_ack);
+	return evlist__parse_control(str, &opts->ctl_fd, &opts->ctl_fd_ack, &opts->ctl_fd_close);
+}
+
+static void close_control_option(struct record_opts *opts)
+{
+	if (opts->ctl_fd_close) {
+		opts->ctl_fd_close = false;
+		close(opts->ctl_fd);
+		if (opts->ctl_fd_ack >= 0)
+			close(opts->ctl_fd_ack);
+	}
 }
 
 static void switch_output_size_warn(struct record *rec)
@@ -2578,9 +2588,10 @@ static struct option __record_options[] = {
 		"libpfm4 event selector. use 'perf list' to list available events",
 		parse_libpfm_events_option),
 #endif
-	OPT_CALLBACK(0, "control", &record.opts, "fd:ctl-fd[,ack-fd]",
+	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"
-		     "\t\t\t  Optionally send control command completion ('ack\\n') to ack-fd descriptor.",
+		     "\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),
 	OPT_END()
 };
@@ -2653,12 +2664,14 @@ int cmd_record(int argc, const char **argv)
 	    !perf_can_record_switch_events()) {
 		ui__error("kernel does not support recording context switch events\n");
 		parse_options_usage(record_usage, record_options, "switch-events", 0);
-		return -EINVAL;
+		err = -EINVAL;
+		goto out_opts;
 	}
 
 	if (switch_output_setup(rec)) {
 		parse_options_usage(record_usage, record_options, "switch-output", 0);
-		return -EINVAL;
+		err = -EINVAL;
+		goto out_opts;
 	}
 
 	if (rec->switch_output.time) {
@@ -2669,8 +2682,10 @@ int cmd_record(int argc, const char **argv)
 	if (rec->switch_output.num_files) {
 		rec->switch_output.filenames = calloc(sizeof(char *),
 						      rec->switch_output.num_files);
-		if (!rec->switch_output.filenames)
-			return -EINVAL;
+		if (!rec->switch_output.filenames) {
+			err = -EINVAL;
+			goto out_opts;
+		}
 	}
 
 	/*
@@ -2686,7 +2701,8 @@ int cmd_record(int argc, const char **argv)
 		rec->affinity_mask.bits = bitmap_alloc(rec->affinity_mask.nbits);
 		if (!rec->affinity_mask.bits) {
 			pr_err("Failed to allocate thread mask for %zd cpus\n", rec->affinity_mask.nbits);
-			return -ENOMEM;
+			err = -ENOMEM;
+			goto out_opts;
 		}
 		pr_debug2("thread mask[%zd]: empty\n", rec->affinity_mask.nbits);
 	}
@@ -2817,6 +2833,8 @@ out:
 	evlist__delete(rec->evlist);
 	symbol__exit();
 	auxtrace_record__free(rec->itr);
+out_opts:
+	close_control_option(&rec->opts);
 	return err;
 }
 

tools/perf/builtin-stat.c

@@ -1047,7 +1047,17 @@ static int parse_control_option(const struct option *opt,
 {
 	struct perf_stat_config *config = opt->value;
 
-	return evlist__parse_control(str, &config->ctl_fd, &config->ctl_fd_ack);
+	return evlist__parse_control(str, &config->ctl_fd, &config->ctl_fd_ack, &config->ctl_fd_close);
+}
+
+static void close_control_option(struct perf_stat_config *config)
+{
+	if (config->ctl_fd_close) {
+		config->ctl_fd_close = false;
+		close(config->ctl_fd);
+		if (config->ctl_fd_ack >= 0)
+			close(config->ctl_fd_ack);
+	}
 }
 
 static struct option stat_options[] = {
@@ -1153,9 +1163,10 @@ static struct option stat_options[] = {
 		"libpfm4 event selector. use 'perf list' to list available events",
 		parse_libpfm_events_option),
 #endif
-	OPT_CALLBACK(0, "control", &stat_config, "fd:ctl-fd[,ack-fd]",
+	OPT_CALLBACK(0, "control", &stat_config, "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"
-		     "\t\t\t  Optionally send control command completion ('ack\\n') to ack-fd descriptor.",
+		     "\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),
 	OPT_END()
 };
@@ -2398,6 +2409,7 @@ out:
 
 	metricgroup__rblist_exit(&stat_config.metric_events);
 	runtime_stat_delete(&stat_config);
+	close_control_option(&stat_config);
 
 	return status;
 }

tools/perf/util/evlist.c

@@ -1727,12 +1727,63 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evsel_list,
 	return leader;
 }
 
-int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack)
+static int evlist__parse_control_fifo(const char *str, int *ctl_fd, int *ctl_fd_ack, bool *ctl_fd_close)
+{
+	char *s, *p;
+	int ret = 0, fd;
+
+	if (strncmp(str, "fifo:", 5))
+		return -EINVAL;
+
+	str += 5;
+	if (!*str || *str == ',')
+		return -EINVAL;
+
+	s = strdup(str);
+	if (!s)
+		return -ENOMEM;
+
+	p = strchr(s, ',');
+	if (p)
+		*p = '\0';
+
+	/*
+	 * O_RDWR avoids POLLHUPs which is necessary to allow the other
+	 * end of a FIFO to be repeatedly opened and closed.
+	 */
+	fd = open(s, O_RDWR | O_NONBLOCK | O_CLOEXEC);
+	if (fd < 0) {
+		pr_err("Failed to open '%s'\n", s);
+		ret = -errno;
+		goto out_free;
+	}
+	*ctl_fd = fd;
+	*ctl_fd_close = true;
+
+	if (p && *++p) {
+		/* O_RDWR | O_NONBLOCK means the other end need not be open */
+		fd = open(p, O_RDWR | O_NONBLOCK | O_CLOEXEC);
+		if (fd < 0) {
+			pr_err("Failed to open '%s'\n", p);
+			ret = -errno;
+			goto out_free;
+		}
+		*ctl_fd_ack = fd;
+	}
+
+out_free:
+	free(s);
+	return ret;
+}
+
+int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack, bool *ctl_fd_close)
 {
 	char *comma = NULL, *endptr = NULL;
 
+	*ctl_fd_close = false;
+
 	if (strncmp(str, "fd:", 3))
-		return -EINVAL;
+		return evlist__parse_control_fifo(str, ctl_fd, ctl_fd_ack, ctl_fd_close);
 
 	*ctl_fd = strtoul(&str[3], &endptr, 0);
 	if (endptr == &str[3])

tools/perf/util/evlist.h

@@ -373,7 +373,7 @@ enum evlist_ctl_cmd {
 	EVLIST_CTL_CMD_ACK
 };
 
-int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack);
+int evlist__parse_control(const char *str, int *ctl_fd, int *ctl_fd_ack, bool *ctl_fd_close);
 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);

tools/perf/util/record.h

@@ -73,6 +73,7 @@ struct record_opts {
 	unsigned int  nr_threads_synthesize;
 	int	      ctl_fd;
 	int	      ctl_fd_ack;
+	bool	      ctl_fd_close;
 };
 
 extern const char * const *record_usage;

tools/perf/util/stat.h

@@ -136,6 +136,7 @@ struct perf_stat_config {
 	struct rblist		 metric_events;
 	int			 ctl_fd;
 	int			 ctl_fd_ack;
+	bool			 ctl_fd_close;
 };
 
 void perf_stat__set_big_num(int set);