linux-kernel - [PATCH 02/19] perf ftrace: detect workload failure

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Date:   Sun, 10 May 2020 23:06:11 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Jiri Olsa <jolsa@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Changbin Du <changbin.du@...il.com>
Subject: [PATCH 02/19] perf ftrace: detect workload failure

Currently there's no error message prompted if we failed to start workload.
And we still get some trace which is confusing. Let's tell users what
happened.

Signed-off-by: Changbin Du <changbin.du@...il.com>
---
 tools/perf/builtin-ftrace.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c
index 11fc02037899..5584f8dec25d 100644
--- a/tools/perf/builtin-ftrace.c
+++ b/tools/perf/builtin-ftrace.c
@@ -45,6 +45,7 @@ struct filter_entry {
 	char			name[];
 };
 
+static volatile int workload_exec_errno;
 static bool done;
 
 static void sig_handler(int sig __maybe_unused)
@@ -63,7 +64,7 @@ static void ftrace__workload_exec_failed_signal(int signo __maybe_unused,
 						siginfo_t *info __maybe_unused,
 						void *ucontext __maybe_unused)
 {
-	/* workload_exec_errno = info->si_value.sival_int; */
+	workload_exec_errno = info->si_value.sival_int;
 	done = true;
 }
 
@@ -382,6 +383,14 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 
 	write_tracing_file("tracing_on", "0");
 
+	if (workload_exec_errno) {
+		const char *emsg = str_error_r(workload_exec_errno, buf, sizeof(buf));
+		/* flush stdout first so below error msg appears at the end. */
+		fflush(stdout);
+		pr_err("workload failed: %s\n", emsg);
+		goto out_close_fd;
+	}
+
 	/* read remaining buffer contents */
 	while (true) {
 		int n = read(trace_fd, buf, sizeof(buf));
@@ -396,7 +405,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 out_reset:
 	reset_tracing_files(ftrace);
 out:
-	return done ? 0 : -1;
+	return (done && !workload_exec_errno) ? 0 : -1;
 }
 
 static int perf_ftrace_config(const char *var, const char *value, void *cb)
-- 
2.25.1