perf tool: improve error handling in perf_flag_probe()

Hi,

Following the EBUSY errors reported by Jiri Olsa [1], I've tryed to improve a bit the way perf_flag_probe() handle errors.

In case EBUSY is returned by perf_event_open(), testing the function again without PERF_FLAG_FD_CLOEXEC is meaningless: EBUSY is not related to close-on-exec flag, so there's nothing to confirm.

For other errors, not yet explicitly handled by perf_flag_probe(), it's pointless to report a second error message for the same error
code: the second check should not print an error if the error is the same as the one returned for the first check.

Changes from v1 [2]:
- resend

Changes from v0 [3]:
- rebased on top of commit 48536c9195ae ("perf tools: Fix probing for PERF_FLAG_FD_CLOEXEC flag");
- update a bit commit message;
- the previous patchset was acked by Jiri[4], but I haven't
reported Acked-by: in this updated patchset.

[1] http://lkml.kernel.org/r/[email protected]
[2] http://lkml.kernel.org/r/[email protected]
[3] http://lkml.kernel.org/r/[email protected]
[4] http://lkml.kernel.org/r/[email protected]

Yann Droneaud (2):
perf tools: shortcut PERF_FLAG_FD_CLOEXEC probing in case of EBUSY
error
perf tools: report PERF_FLAG_FD_CLOEXEC probing error once

 tools/perf/util/cloexec.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

2.4.3