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>

1 files changed, 53 insertions, 2 deletions

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 47d1045a19af..00593e5f2a9d 100644
--- a/tools/perf/util/evlist.c
+++ b/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])