linux-kernel - [PATCH 1/5] ftrace perf: Check sample types only for sampling events

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Date:	Wed,  9 Mar 2016 21:46:41 +0100
From:	Jiri Olsa <jolsa@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: [PATCH 1/5] ftrace perf: Check sample types only for sampling events

Currently we check sample type for ftrace:function event
even if it's not created as sampling event. That prevents
creating ftrace_function event in counting mode.

Making sure we check sample types only for sampling events.

Before:
  $ sudo perf stat -e ftrace:function ls
  ...

   Performance counter stats for 'ls':

     <not supported>      ftrace:function

         0.001983662 seconds time elapsed

After:
  $ sudo perf stat -e ftrace:function ls
  ...

   Performance counter stats for 'ls':

              44,498      ftrace:function

         0.037534722 seconds time elapsed

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 kernel/trace/trace_event_perf.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
index 00df25fd86ef..a7171ec2c1ca 100644
--- a/kernel/trace/trace_event_perf.c
+++ b/kernel/trace/trace_event_perf.c
@@ -52,14 +52,14 @@ static int perf_trace_event_perm(struct trace_event_call *tp_event,
 		 * event, due to issues with page faults while tracing page
 		 * fault handler and its overall trickiness nature.
 		 */
-		if (!p_event->attr.exclude_callchain_user)
+		if (is_sampling_event(p_event) && !p_event->attr.exclude_callchain_user)
 			return -EINVAL;
 
 		/*
 		 * Same reason to disable user stack dump as for user space
 		 * callchains above.
 		 */
-		if (p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
+		if (is_sampling_event(p_event) && p_event->attr.sample_type & PERF_SAMPLE_STACK_USER)
 			return -EINVAL;
 	}
 
-- 
2.4.3