[PATCH 18/23] perf ftrace: Show error message when fails to set ftrace files

Arnaldo Carvalho de Melo
2017-06-20T01:58:24Z

From: Namhyung Kim <namhyung@kernel.org>

It'd be better for debugging to show an error message when it fails to
setup ftrace for some reason.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: kernel-team@lge.com
Link: http://lkml.kernel.org/r/20170618142302.25390-1-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-ftrace.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 9e0b35cd0eea..966a94fa8200 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -61,6 +61,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append)
int fd, ret = -1;
ssize_t size = strlen(val);
int flags = O_WRONLY;
+ char errbuf[512];

file = get_tracing_file(name);
if (!file) {
@@ -75,14 +76,16 @@ static int __write_tracing_file(const char *name, const char *val, bool append)

fd = open(file, flags);
if (fd < 0) {
- pr_debug("cannot open tracing file: %s\n", name);
+ pr_debug("cannot open tracing file: %s: %s\n",
+ name, str_error_r(errno, errbuf, sizeof(errbuf)));
goto out;
}

if (write(fd, val, size) == size)
ret = 0;
else
- pr_debug("write '%s' to tracing/%s failed\n", val, name);
+ pr_debug("write '%s' to tracing/%s failed: %s\n",
+ val, name, str_error_r(errno, errbuf, sizeof(errbuf)));

close(fd);
out:
--
2.9.4