Revert r122552: "Implement proper atomic code for trace macros."

The tsan bots have been red since this change, and crashing on
WorkerPoolTest.PostTask in base.  I've been unable to reproduce the failure
from the bots locally, so I'm reverting this and we'll see what happens on the
bots.

Unfortunately we don't have a win_tsan try bot, or I'd say reapply once you get
a green run from that.

TBR=jbates@chromium.org
BUG=115107
TEST=base_unittests.exe

Review URL: https://chromiumcodereview.appspot.com/9430018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@122881 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 15 insertions, 22 deletions

diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index 5860f8d..2298b03 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -145,6 +145,9 @@
 // Without the use of these static category pointers and enabled flags all
 // trace points would carry a significant performance cost of aquiring a lock
 // and resolving the category.
+//
+// ANNOTATE_BENIGN_RACE is used to suppress the warning on the static category
+// pointers.
 
 
 #ifndef BASE_DEBUG_TRACE_EVENT_H_
@@ -153,9 +156,8 @@
 
 #include <string>
 
-#include "base/atomicops.h"
-#include "base/debug/trace_event_impl.h"
 #include "build/build_config.h"
+#include "base/debug/trace_event_impl.h"
 
 // By default, const char* argument values are assumed to have long-lived scope
 // and will not be copied. Use this macro to force a const char* to be copied.
@@ -483,21 +485,14 @@
     INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
 
 // Implementation detail: internal macro to create static category.
-// No barriers are needed, because this code is designed to operate safely
-// even when the unsigned char* points to garbage data (which may be the case
-// on processors without cache coherency).
+// - ANNOTATE_BENIGN_RACE, see Thread Safety above.
 #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category) \
-    static base::subtle::AtomicWord INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
-    const uint8* INTERNAL_TRACE_EVENT_UID(catstatic) = \
-        reinterpret_cast<const uint8*>( \
-            base::subtle::NoBarrier_Load(&INTERNAL_TRACE_EVENT_UID(atomic))); \
-    if (!INTERNAL_TRACE_EVENT_UID(catstatic)) { \
+    static const unsigned char* INTERNAL_TRACE_EVENT_UID(catstatic) = NULL; \
+    ANNOTATE_BENIGN_RACE(&INTERNAL_TRACE_EVENT_UID(catstatic), \
+                         "trace_event category"); \
+    if (!INTERNAL_TRACE_EVENT_UID(catstatic)) \
       INTERNAL_TRACE_EVENT_UID(catstatic) = \
-          TRACE_EVENT_API_GET_CATEGORY_ENABLED(category); \
-      base::subtle::NoBarrier_Store(&INTERNAL_TRACE_EVENT_UID(atomic), \
-          reinterpret_cast<base::subtle::AtomicWord>( \
-              INTERNAL_TRACE_EVENT_UID(catstatic))); \
-    }
+          TRACE_EVENT_API_GET_CATEGORY_ENABLED(category);
 
 // Implementation detail: internal macro to create static category and add
 // event if the category is enabled.
diff --git a/base/debug/trace_event_impl.cc b/base/debug/trace_event_impl.cc
index b81e32a..f1c80bd 100644
--- a/base/debug/trace_event_impl.cc
+++ b/base/debug/trace_event_impl.cc
@@ -20,7 +20,6 @@
 #include "base/utf_string_conversions.h"
 #include "base/stl_util.h"
 #include "base/sys_info.h"
-#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/time.h"
 
 #if defined(OS_WIN)
@@ -325,12 +324,6 @@ TraceLog::TraceLog()
     : enabled_(false)
     , dispatching_to_observer_list_(false) {
   SetProcessID(static_cast<int>(base::GetCurrentProcId()));
-  // Trace is enabled or disabled on one thread while other threads are
-  // accessing the enabled flag. We don't care whether edge-case events are
-  // traced or not, so we allow races on the enabled flag to keep the trace
-  // macros fast.
-  ANNOTATE_BENIGN_RACE_SIZED(g_category_enabled, sizeof(g_category_enabled),
-                             "trace_event category enabled");
 }
 
 TraceLog::~TraceLog() {
@@ -369,6 +362,8 @@ static void EnableMatchingCategory(int category_index,
     if (is_match)
       break;
   }
+  ANNOTATE_BENIGN_RACE(&g_category_enabled[category_index],
+                       "trace_event category enabled");
   g_category_enabled[category_index] = is_match ?
       is_included : (is_included ^ 1);
 }
@@ -407,6 +402,8 @@ const unsigned char* TraceLog::GetCategoryEnabledInternal(const char* name) {
       else
         EnableMatchingCategory(new_index, excluded_categories_, 0);
     } else {
+      ANNOTATE_BENIGN_RACE(&g_category_enabled[new_index],
+                           "trace_event category enabled");
       g_category_enabled[new_index] = 0;
     }
     return &g_category_enabled[new_index];
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index 1806f893..c1d98b8 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -18,6 +18,7 @@
 #include "base/observer_list.h"
 #include "base/string_util.h"
 #include "base/synchronization/lock.h"
+#include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/timer.h"
 
 // Older style trace macros with explicit id and extra data