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

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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

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[GIT PULL 00/23] perf/core improvements and fixes Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 09/23] tools: Adopt noinline from kernel sources Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 11/23] tools: Adopt __aligned from kernel sources Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 08/23] perf tools: Use __maybe_unused consistently Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 05/23] tools: Adopt __noreturn from kernel sources Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 18/23] perf ftrace: Show error message when fails to set ftrace files Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 03/23] perf config: Invert an if statement to reduce nesting in cmd_config() Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 19/23] perf ftrace: Move setup_pager before opening trace_pipe Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 13/23] perf intel-pt/bts: Remove unused SAMPLE_SIZE defines and bts priv array Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:00 +0200
  [PATCH 12/23] perf coresight: Remove superfluous check before use Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:10 +0200
  [PATCH 06/23] tools: Adopt __printf from kernel sources Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:10 +0200
  [PATCH 17/23] perf script: Support -F brstackoff,dso Arnaldo Carvalho de Melo <acme@kernel.org> - 2017-06-20 04:10 +0200
  Re: [GIT PULL 00/23] perf/core improvements and fixes Ingo Molnar <mingo@kernel.org> - 2017-06-20 11:00 +0200

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