linux-kernel - [PATCH 2/2] perf tools: report PERF_FLAG_FD

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Date:	Sat, 13 Sep 2014 10:46:24 +0200
From:	Yann Droneaud <ydroneaud@...eya.com>
To:	linux-kernel@...r.kernel.org
Cc:	Yann Droneaud <ydroneaud@...eya.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	William Cohen <wcohen@...hat.com>
Subject: [PATCH 2/2] perf tools: report PERF_FLAG_FD_CLOEXEC probing error once

In case of failure, unrelated to PERF_FLAG_FD_CLOEXEC,
perf_flag_probe() reports the error twice. For example:

  $ perf record ls
  Error:
  perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error 16 (Device or resource busy)
  perf_event_open(..., 0) failed unexpectedly with error 16 (Device or resource busy)

There's no need for the second error message, so this
patch changes the function to only report a second
error message when the two calls to perf_even_open(2)
fail with different error codes.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...il.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: William Cohen <wcohen@...hat.com>
Reported-by: Jiri Olsa <jolsa@...nel.org>
Link: http://lkml.kernel.org/r/1406908014-8312-1-git-send-email-jolsa@kernel.org
Link: http://lkml.kernel.org/r/cover.1410595700.git.ydroneaud@opteya.com
Signed-off-by: Yann Droneaud <ydroneaud@...eya.com>
---
 tools/perf/util/cloexec.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 6b948e05e5f0..91331b4ffc3d 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -16,7 +16,7 @@ static int perf_flag_probe(void)
 		.exclude_kernel = 1,
 	};
 	int fd;
-	int err;
+	int err0, err1;
 	int cpu;
 	pid_t pid = -1;
 	char sbuf[STRERR_BUFSIZE];
@@ -35,7 +35,7 @@ static int perf_flag_probe(void)
 		}
 		break;
 	}
-	err = errno;
+	err0 = errno;
 
 	if (fd >= 0) {
 		close(fd);
@@ -43,25 +43,27 @@ static int perf_flag_probe(void)
 	}
 
 	/* ignore busy errors */
-	if (err == EBUSY)
+	if (err0 == EBUSY)
 		return -1;
 
-	WARN_ONCE(err != EINVAL,
+	WARN_ONCE(err0 != EINVAL,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
-		  err, strerror_r(err, sbuf, sizeof(sbuf)));
+		  err0, strerror_r(err0, sbuf, sizeof(sbuf)));
 
 	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
 	fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
-	err = errno;
+	err1 = errno;
 
-	if (WARN_ONCE(fd < 0,
-		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
-		      err, strerror_r(err, sbuf, sizeof(sbuf))))
-		return -1;
+	if (fd >= 0) {
+		close(fd);
+		return 0;
+	}
 
-	close(fd);
+	WARN_ONCE(err0 != err1,
+		  "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
+		  err1, strerror_r(err1, sbuf, sizeof(sbuf)));
 
-	return 0;
+	return -1;
 }
 
 unsigned long perf_event_open_cloexec_flag(void)
-- 
1.9.3

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