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Subject[PATCH 2/5] perf: Annotate lock context on perf_output_begin/end()
Date
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@gmail.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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