linux-kernel - [RFC 2/2] perf/core: change errno for sampling event not supported in hardware

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Message-ID: <1462786660-2900-3-git-send-email-vgupta@synopsys.com>
Date:	Mon, 9 May 2016 15:07:40 +0530
From:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:	<linux-perf-users@...r.kernel.org>, <peterz@...radead.org>,
	<acme@...hat.com>
CC:	<linux-snps-arc@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <mingo@...nel.org>,
	<vincent.weaver@...ne.edu>,
	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Subject: [RFC 2/2] perf/core: change errno for sampling event not supported in hardware

This allows userspace to identify this case specifically from the
catch all error msg it prints currently.

This is an ABI change

Before
-------
| # perf record ls
| Error:
| The sys_perf_event_open() syscall returned with 524 (Unknown error 524)
| for event (cycles:ppp).
| /bin/dmesg may provide additional information.
| No CONFIG_PERF_EVENTS=y kernel support configured?

Now
-------
| # perf record ls
| Error:
| PMU Hardware doesn't support sampling/overflow-interrupts.

Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4e2ebf6f2f1f..41c5c7122987 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8435,7 +8435,7 @@ SYSCALL_DEFINE5(perf_event_open,
 
 	if (is_sampling_event(event)) {
 		if (event->pmu->capabilities & PERF_PMU_CAP_NO_INTERRUPT) {
-			err = -ENOTSUPP;
+			err = -EOPNOTSUPP;
 			goto err_alloc;
 		}
 	}
-- 
2.5.0