Earlier, when 'timechart record' was invoked by a user without
permissions to debugfs:
$ perf timechart record
invalid or unsupported event: 'power:cpu_frequency'
Run 'perf list' for a list of valid events
usage: perf record [<options>] [<command>]
or: perf record [<options>] -- <command> [<options>]
[... detailed usage information ...]
This is highly user unfriendly, as the real problem is not reported to
the user correctly. Now, the user gets a much more friendly:
$ perf timechart record
Error: No permissions to read $debugfs/tracing/events/power/cpu_frequency
Hint: Change the permissions of debugfs: /sys/kernel/debug
The directory will be present if your kernel was compiled with debugfs
support.
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Arnaldo Carvalho de Melo <a...@ghostprotocols.net>
Signed-off-by: Ramkumar Ramachandra <artag...@gmail.com>
---
tools/perf/builtin-timechart.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/tools/perf/builtin-timechart.c b/tools/perf/builtin-timechart.c
index c2e0231..ceaf9b8 100644
--- a/tools/perf/builtin-timechart.c
+++ b/tools/perf/builtin-timechart.c
@@ -1056,6 +1056,14 @@ static int __cmd_record(int argc, const char **argv)
}
#endif
+ /* Perform a quick sanity check */
+ if (!is_valid_tracepoint("power:cpu_frequency")) {
+ fprintf(stderr, "Error:\tNo permissions to read
$debugfs/tracing/events/power/cpu_frequency\n");
+ fprintf(stderr, "Hint:\tChange the permissions of debugfs:
/sys/kernel/debug\n");
+ fprintf(stderr, "\tThe directory will be present if your kernel
was compiled with debugfs support.\n");
+ return 1;
+ }
+
rec_argc = record_elems + argc - 1;
rec_argv = calloc(rec_argc + 1, sizeof(char *));
--
1.8.4.477.g5d89aa9
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