linux-kernel - [PATCH 2/4] perf ftrace: Move setup_pager before opening trace

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Date:   Sun, 18 Jun 2017 23:23:00 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Frederic Weisbecker <fweisbec@...il.com>
Subject: [PATCH 2/4] perf ftrace: Move setup_pager before opening trace_pipe

The perf ftrace fails to reset tracer after finish the recording like
below:

  $ sudo perf ftrace -v hello
  write 'nop' to tracing/current_tracer failed: Device or resource busy
  ...

This is because the trace_pipe file is open in pager process.  Move the
pager setup before opening the file.

Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Fixes: 583359646fde ("perf ftrace: Use pager for displaying result")
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/builtin-ftrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 966a94fa8200..982b98ee639e 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -231,6 +231,8 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_reset;
 	}
 
+	setup_pager();
+
 	trace_file = get_tracing_file("trace_pipe");
 	if (!trace_file) {
 		pr_err("failed to open trace_pipe\n");
@@ -254,8 +256,6 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		goto out_close_fd;
 	}
 
-	setup_pager();
-
 	perf_evlist__start_workload(ftrace->evlist);
 
 	while (!done) {
-- 
2.13.0