perf tools: Show event fd in debug output

It is useful for debug to see file descriptors for each event.

Before:

  $ perf stat -vvv -e cycles,cache-misses ls
  ...
  sys_perf_event_open: pid 12146  cpu -1  group_fd -1  flags 0x8
  ...
  sys_perf_event_open: pid 12146  cpu -1  group_fd 3  flags 0x8
  sys_perf_event_open failed, error -13

Now:

  $ perf stat -vvv -e cycles,cache-misses ls
  ...
  sys_perf_event_open: pid 12858  cpu -1  group_fd -1  flags 0x8 = 3
  ...
  sys_perf_event_open: pid 12858  cpu -1  group_fd 3  flags 0x8
  sys_perf_event_open failed, error -13

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1479764011-10732-2-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/evsel.c

@@ -1481,7 +1481,7 @@ retry_sample_id:
 
 			group_fd = get_group_fd(evsel, cpu, thread);
 retry_open:
-			pr_debug2("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx\n",
+			pr_debug2("sys_perf_event_open: pid %d  cpu %d  group_fd %d  flags %#lx",
 				  pid, cpus->map[cpu], group_fd, flags);
 
 			FD(evsel, cpu, thread) = sys_perf_event_open(&evsel->attr,
@@ -1490,11 +1490,13 @@ retry_open:
 								     group_fd, flags);
 			if (FD(evsel, cpu, thread) < 0) {
 				err = -errno;
-				pr_debug2("sys_perf_event_open failed, error %d\n",
+				pr_debug2("\nsys_perf_event_open failed, error %d\n",
 					  err);
 				goto try_fallback;
 			}
 
+			pr_debug2(" = %d\n", FD(evsel, cpu, thread));
+
 			if (evsel->bpf_fd >= 0) {
 				int evt_fd = FD(evsel, cpu, thread);
 				int bpf_fd = evsel->bpf_fd;