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Message-Id: <1441987205-4021-4-git-send-email-alexander.shishkin@linux.intel.com>
Date: Fri, 11 Sep 2015 19:00:02 +0300
From: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To: Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org, vince@...ter.net, eranian@...gle.com,
johannes@...solutions.net,
Arnaldo Carvalho de Melo <acme@...radead.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH RFC v3 3/6] perf/x86: Annotate a BTS error with extended error reporting
Old-style BTS driver does not support kernel tracing, which normally
would be visible to userspace as -EOPNOTSUPP, or from the tool's user's
perspective:
> # perf record -e branches -c1 ls
> Error:
> No hardware sampling interrupt available.
> No APIC? If so then you can boot the kernel with the "lapic" boot parameter to force-enable it.
but with the new way of reporting errors, they will see the following:
> # perf record -e branches -c1 ls
> Error:
> Syscall returned -95, becasue BTS sampling not allowed for kernel space.
> Offending attribute field: "exclude_kernel"
which is somewhat more to the point of what has actually transpired.
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
arch/x86/kernel/cpu/perf_event.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index f56cf074d0..e3d953ef49 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -12,6 +12,8 @@
* For licencing details see kernel-base/COPYING
*/
+#define EXTERR_MODNAME "perf/x86"
+
#include <linux/perf_event.h>
#include <linux/capability.h>
#include <linux/notifier.h>
@@ -426,7 +428,8 @@ int x86_setup_perfctr(struct perf_event *event)
/* BTS is currently only allowed for user-mode. */
if (!attr->exclude_kernel)
- return -EOPNOTSUPP;
+ return perf_err(-EOPNOTSUPP, exclude_kernel,
+ "BTS sampling not allowed for kernel space");
/* disallow bts if conflicting events are present */
if (x86_add_exclusive(x86_lbr_exclusive_lbr))
--
2.5.1
--
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