[PATCH 1/2] perf tools: shortcut PERF_FLAG_FD_CLOEXEC probing in case of EBUSY error

From: Yann Droneaud
Date: Sat Sep 13 2014 - 06:39:53 EST


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@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/1406908014-8312-1-git-send-email-jolsa@xxxxxxxxxx
Link: http://lkml.kernel.org/r/cover.1410595700.git.ydroneaud@xxxxxxxxxx
Signed-off-by: Yann Droneaud <ydroneaud@xxxxxxxxxx>
---
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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