linux-kernel - [PATCH 2/5] perf: Annotate lock context on perf_output

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Date:	Mon, 27 Sep 2010 19:39:54 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] perf: Annotate lock context on perf_output_begin/end()

perf_output_begin() conditionally grabs RCU read lock in case of
returning 0. Rename and wrap it using __cond_lock() to annotate
this. Although perf_output_begin() returns 0 or error code, IMHO
converting it to boolean will not be a problem since there is no
user takes account of the actual code. Annotate perf_output_end()
also.

Signed-off-by: Namhyung Kim <namhyung@...il.com>
---
 include/linux/perf_event.h |    6 +++++-
 kernel/perf_event.c        |    3 ++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 716f99b..167dd3d 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1009,9 +1009,13 @@ extern void perf_bp_event(struct perf_event *event, void *data);
 #define perf_instruction_pointer(regs)	instruction_pointer(regs)
 #endif
 
-extern int perf_output_begin(struct perf_output_handle *handle,
+extern int __perf_output_begin(struct perf_output_handle *handle,
 			     struct perf_event *event, unsigned int size,
 			     int nmi, int sample);
+
+#define perf_output_begin(h, e, s, n, sp)				\
+	(!__cond_lock(RCU, !__perf_output_begin(h, e, s, n, sp)))
+
 extern void perf_output_end(struct perf_output_handle *handle);
 extern void perf_output_copy(struct perf_output_handle *handle,
 			     const void *buf, unsigned int len);
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index c058a42..bd5d750 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3106,7 +3106,7 @@ __always_inline void perf_output_copy(struct perf_output_handle *handle,
 	} while (len);
 }
 
-int perf_output_begin(struct perf_output_handle *handle,
+int __perf_output_begin(struct perf_output_handle *handle,
 		      struct perf_event *event, unsigned int size,
 		      int nmi, int sample)
 {
@@ -3190,6 +3190,7 @@ out:
 }
 
 void perf_output_end(struct perf_output_handle *handle)
+	__releases(RCU)
 {
 	struct perf_event *event = handle->event;
 	struct perf_buffer *buffer = handle->buffer;
-- 
1.7.2.2

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