linux-kernel - Re: [PATCH] perf stat: Do not show stats if workload fails

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Date:	Tue, 24 Dec 2013 10:30:03 -0300
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	David Ahern <dsahern@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH] perf stat: Do not show stats if workload fails

Em Tue, Dec 24, 2013 at 09:53:42AM -0300, Arnaldo Carvalho de Melo escreveu:
> The thing to check is perf_evlist__{prepare,start}_workload notification
> errors using SIGUSR1, that we need to check for in the caller, and emit
> the message, no?

Something like this:

1. We tell perf_evlist__prepare_workload that we want a signal if execvp
fails, it will be a SIGUSR1

2. We catch that signal in 'stat' and check that we got a signal, only
problem so far with this signal maze is that we're getting a SIGCHLD
while I was expecting a SIGUSR1... I.e. the "if (signr != -1) test
really should be if (signr == SIGUSR1), but I'm getting a SIGCHLD there
and the elves are tugging me away...

- Arnaldo

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index dab98b50c9fe..d2350fef8cde 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -144,6 +144,7 @@ static struct timespec		ref_time;
 static struct cpu_map		*aggr_map;
 static int			(*aggr_get_id)(struct cpu_map *m, int cpu);
 
+static volatile int signr = -1;
 static volatile int done = 0;
 
 struct perf_stat {
@@ -531,7 +532,7 @@ static int __run_perf_stat(int argc, const char **argv)
 
 	if (forks) {
 		if (perf_evlist__prepare_workload(evsel_list, &target, argv,
-						  false, false) < 0) {
+						  false, true) < 0) {
 			perror("failed to prepare workload");
 			return -1;
 		}
@@ -598,6 +599,8 @@ static int __run_perf_stat(int argc, const char **argv)
 		wait(&status);
 		if (WIFSIGNALED(status))
 			psignal(WTERMSIG(status), argv[0]);
+		else if (signr != -1)
+			return -1;
 	} else {
 		handle_initial_delay();
 		while (!done) {
@@ -1335,8 +1338,6 @@ static void print_stat(int argc, const char **argv)
 	}
 }
 
-static volatile int signr = -1;
-
 static void skip_signal(int signo)
 {
 	if ((child_pid == -1) || interval)
@@ -1785,6 +1786,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __maybe_unused)
 	signal(SIGCHLD, skip_signal);
 	signal(SIGALRM, skip_signal);
 	signal(SIGABRT, skip_signal);
+	signal(SIGUSR1, skip_signal);
 
 	status = 0;
 	for (run_idx = 0; forever || run_idx < run_count; run_idx++) {
--
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