linux-kernel - [PATCH 1/2] perf tools: shortcut PERF_FLAG_FD

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Date:	Sat, 13 Sep 2014 10:25:32 +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 1/2] perf tools: shortcut PERF_FLAG_FD_CLOEXEC probing in case of EBUSY error

This patch is a simplification of the logic introduced as part of
commit 63914aca8f7e7a75d0ee027af7b1755c69cc1e2c ('perf tools: Show
better error message in case we fail to open counters due to EBUSY
error'): if EBUSY is reported by perf_event_open(), it will not be
possible to probe PERF_FLAG_FD_CLOEXEC, so it's safe to leave early.

Note that EBUSY errors are not really expected here since commit
038fa0b9739d7f375f3f61a2ce4f78ad44329f66 ('perf tools: Fix
PERF_FLAG_FD_CLOEXEC flag probing event type open counters due to
EBUSY error'): the perf event type used now should be safe to use
regarding -EBUSY error.

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>
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 | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
index 47b78b3f0325..6b948e05e5f0 100644
--- a/tools/perf/util/cloexec.c
+++ b/tools/perf/util/cloexec.c
@@ -42,7 +42,11 @@ static int perf_flag_probe(void)
 		return 1;
 	}
 
-	WARN_ONCE(err != EINVAL && err != EBUSY,
+	/* ignore busy errors */
+	if (err == EBUSY)
+		return -1;
+
+	WARN_ONCE(err != EINVAL,
 		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
 		  err, strerror_r(err, sbuf, sizeof(sbuf)));
 
@@ -50,7 +54,7 @@ static int perf_flag_probe(void)
 	fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
 	err = errno;
 
-	if (WARN_ONCE(fd < 0 && err != EBUSY,
+	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;
-- 
1.9.3

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