utils: clarify scoped tracing functionality

ScopedTrace objects were being used in place of ATRACE_NAME because of a
misunderstanding of it's function.  Cleared up documentation for usage.

Also explicitly use global namespace for sysprop callback.

Change-Id: I7c248b486b614ccdb841659ca0dcfc644fda670a

2 files changed, 6 insertions, 9 deletions

diff --git a/include/utils/Trace.h b/include/utils/Trace.h
index 940aec1ce7..49578c47df 100644
--- a/include/utils/Trace.h
+++ b/include/utils/Trace.h
@@ -31,15 +31,12 @@
 
 // See <cutils/trace.h> for more ATRACE_* macros.
 
-// ATRACE_CALL traces the beginning and end of the current function.  To trace
-// the correct start and end times this macro should be the first line of the
-// function body.
-#define ATRACE_CALL() android::ScopedTrace ___tracer(ATRACE_TAG, __FUNCTION__)
-
-// ATRACE_NAME traces the beginning and end of the current function.  To trace
-// the correct start and end times this macro should be the first line of the
-// function body.
+// ATRACE_NAME traces the beginning and end of the current scope.  To trace
+// the correct start and end times this macro should be declared first in the
+// scope body.
 #define ATRACE_NAME(name) android::ScopedTrace ___tracer(ATRACE_TAG, name)
+// ATRACE_CALL is an ATRACE_NAME that uses the current function name.
+#define ATRACE_CALL() ATRACE_NAME(__FUNCTION__)
 
 namespace android {
 
diff --git a/libs/utils/Trace.cpp b/libs/utils/Trace.cpp
index d4f02187fd..36fd802146 100644
--- a/libs/utils/Trace.cpp
+++ b/libs/utils/Trace.cpp
@@ -21,5 +21,5 @@ static void traceInit() __attribute__((constructor));
 
 static void traceInit()
 {
-    android::add_sysprop_change_callback(atrace_update_tags, 0);
+    ::android::add_sysprop_change_callback(atrace_update_tags, 0);
 }