[PATCH v2 2/2] perf tools: report PERF_FLAG_FD_CLOEXEC probing error once

[Yann Droneaud]

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@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: William Cohen <wcohen@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/cover.1443708092.git.ydroneaud@xxxxxxxxxx
Reported-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
---
 tools/perf/util/cloexec.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index be226d293c91..552528698566 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -26,7 +26,7 @@ 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];
@@ -49,7 +49,7 @@ static int perf_flag_probe(void)
 		}
 		break;
 	}
-	err = errno;
+	err0 = errno;
 
 	if (fd >= 0) {
 		close(fd);
@@ -57,12 +57,12 @@ 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 */
 	while (1) {
@@ -73,17 +73,18 @@ static int perf_flag_probe(void)
 		}
 		break;
 	}
-	err = errno;
+	err1 = errno;
 
-	if (fd >= 0)
+	if (fd >= 0) {
 		close(fd);
+		return 0;
+	}
 
-	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;
+	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)
-- 
2.4.3

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