tracing: Evaluate len expression only once in __dynamic_array macro

Use a temporary variable to store the expansion of the len expression.
If the evaluation is expensive, this commit will ensure it is evaluated
only once inside ftrace_get_offsets_<call>.

Link: http://lkml.kernel.org/r/1393651938-16418-3-git-send-email-filbranden@google.com
Signed-off-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 2125005..e15ae40 100644 (file)
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -361,10 +361,11 @@ ftrace_define_fields_##call(struct ftrace_event_call *event_call) \
 
 #undef __dynamic_array
 #define __dynamic_array(type, item, len)                               \
+       __item_length = (len) * sizeof(type);                           \
        __data_offsets->item = __data_size +                            \
                               offsetof(typeof(*entry), __data);        \
-       __data_offsets->item |= ((len) * sizeof(type)) << 16;           \
-       __data_size += (len) * sizeof(type);
+       __data_offsets->item |= __item_length << 16;                    \
+       __data_size += __item_length;
 
 #undef __string
 #define __string(item, src) __dynamic_array(char, item,                        \
@@ -376,6 +377,7 @@ static inline notrace int ftrace_get_offsets_##call(                        \
        struct ftrace_data_offsets_##call *__data_offsets, proto)       \
 {                                                                      \
        int __data_size = 0;                                            \
+       int __maybe_unused __item_length;                               \
        struct ftrace_raw_##call __maybe_unused *entry;                 \
                                                                        \
        tstruct;                                                        \