[PATCH 1/5] perf/sdt: Show proper hint

[Ravi Bangoria]

All events from 'perf list', except SDT events, can be directly
recorded with 'perf record'. But, the flow is little different
for SDT events. User has to probe on SDT events before recording
them. Perf is showing misleading message when user tries to
record SDT event without probing it. Show proper hint there.

Before patch:
  $ perf record -a -e sdt_glib:idle__add
    event syntax error: 'sdt_glib:idle__add'
                     \___ unknown tracepoint

    Error:  File /sys/kernel/debug/tracing/events/sdt_glib/idle__add ...
    Hint:   Perhaps this kernel misses some CONFIG_ setting to enable...
    ...

After patch:
  $ perf record -e sdt_glib:main__after_check
    event syntax error: 'sdt_glib:idle__add'
                     \___ unknown tracepoint

    Error:  File /sys/kernel/debug/tracing/events/sdt_glib/idle__add ...
    Hint:   SDT event has to be probed before recording it.

Suggested-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Ravi Bangoria <ravi.bangoria@xxxxxxxxxxxxxxxxxx>
---
 tools/lib/api/fs/tracing_path.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/tools/lib/api/fs/tracing_path.c b/tools/lib/api/fs/tracing_path.c
index 251b7c3..a0e85df 100644
--- a/tools/lib/api/fs/tracing_path.c
+++ b/tools/lib/api/fs/tracing_path.c
@@ -99,10 +99,18 @@ static int strerror_open(int err, char *buf, size_t size, const char *filename)
 		 * - jirka
 		 */
 		if (debugfs__configured() || tracefs__configured()) {
-			snprintf(buf, size,
-				 "Error:\tFile %s/%s not found.\n"
-				 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
-				 tracing_events_path, filename);
+			/* sdt markers */
+			if (!strncmp(filename, "sdt_", 4)) {
+				snprintf(buf, size,
+					"Error:\tFile %s/%s not found.\n"
+					"Hint:\tSDT event has to be probed before recording it.\n",
+					tracing_events_path, filename);
+			} else {
+				snprintf(buf, size,
+					 "Error:\tFile %s/%s not found.\n"
+					 "Hint:\tPerhaps this kernel misses some CONFIG_ setting to enable this feature?.\n",
+					 tracing_events_path, filename);
+			}
 			break;
 		}
 		snprintf(buf, size, "%s",
-- 
2.9.3