Clean up SkDynamicAnnotations.

include/core/SkOnce.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkOnce_DEFINED
 #define SkOnce_DEFINED
 
 // Before trying SkOnce, see if SkLazyPtr or SkLazyFnPtr will work for you.
 // They're smaller and faster, if slightly less versatile.
 
 
 // SkOnce.h defines SK_DECLARE_STATIC_ONCE and SkOnce(), which you can use
 // together to create a threadsafe way to call a function just once.  E.g.
 //
 // static void register_my_stuff(GlobalRegistry* registry) {
 //     registry->register(...);
 // }
 // ...
 // void EnsureRegistered() {
 //     SK_DECLARE_STATIC_ONCE(once);
 //     SkOnce(&once, register_my_stuff, GetGlobalRegistry());
 // }
 //
 // No matter how many times you call EnsureRegistered(), register_my_stuff will be called just once.
 // OnceTest.cpp also should serve as a few other simple examples.
 
-#include "SkDynamicAnnotations.h"
-#include "SkThread.h"
-#include "SkTypes.h"
+#include "SkAtomics.h"
 
 // This must be used in a global scope, not in fuction scope or as a class member.
 #define SK_DECLARE_STATIC_ONCE(name) namespace {} static SkOnceFlag name
 
 class SkOnceFlag;
 
 inline void SkOnce(SkOnceFlag* once, void (*f)());
 
 template <typename Arg>
 inline void SkOnce(SkOnceFlag* once, void (*f)(Arg), Arg arg);
@@ skipping 35 matching lines @@
 // We've pulled a pretty standard double-checked locking implementation apart
 // into its main fast path and a slow path that's called when we suspect the
 // one-time code hasn't run yet.
 
 // This is the guts of the code, called when we suspect the one-time code hasn't been run yet.
 // This should be rarely called, so we separate it from SkOnce and don't mark it as inline.
 // (We don't mind if this is an actual function call, but odds are it'll be inlined anyway.)
 template <typename Lock, typename Arg>
 static void sk_once_slow(bool* done, Lock* lock, void (*f)(Arg), Arg arg) {
     lock->acquire();
-    if (!*done) {
+    if (!sk_atomic_load(done, sk_memory_order_relaxed)) {
         f(arg);
         // Also known as a store-store/load-store barrier, this makes sure that the writes
         // done before here---in particular, those done by calling f(arg)---are observable
         // before the writes after the line, *done = true.
         //
         // In version control terms this is like saying, "check in the work up
         // to and including f(arg), then check in *done=true as a subsequent change".
         //
         // We'll use this in the fast path to make sure f(arg)'s effects are
         // observable whenever we observe *done == true.
         sk_release_store(done, true);
     }
     lock->release();
 }
 
 // This is our fast path, called all the time.  We do really want it to be inlined.
 template <typename Lock, typename Arg>
 inline void SkOnce(bool* done, Lock* lock, void (*f)(Arg), Arg arg) {
-    if (!SK_ANNOTATE_UNPROTECTED_READ(*done)) {
+    // When *done == true:
+    //   Also known as a load-load/load-store barrier, this acquire barrier makes
+    //   sure that anything we read from memory---in particular, memory written by
+    //   calling f(arg)---is at least as current as the value we read from done.
+    //
+    //   In version control terms, this is a lot like saying "sync up to the
+    //   commit where we wrote done = true".
+    //
+    //   The release barrier in sk_once_slow guaranteed that done = true
+    //   happens after f(arg), so by syncing to done = true here we're
+    //   forcing ourselves to also wait until the effects of f(arg) are readble.
+    //
+    // When *done == false:
+    //   We'll try to call f(arg) in sk_once_slow.
+    //   If we get the lock, great, we call f(arg), release true into done, and drop the lock.
+    //   If we race and don't get the lock first, we'll wait for the first guy to finish.
+    //   Then lock acquire() will give us at least an acquire memory barrier to get the same
+    //   effect as the acquire load in the *done == true fast case.  We'll see *done is true,
+    //   then just drop the lock and return.
+    if (!sk_atomic_load(done, sk_memory_order_acquire)) {
         sk_once_slow(done, lock, f, arg);
     }
-    // Also known as a load-load/load-store barrier, this acquire barrier makes
-    // sure that anything we read from memory---in particular, memory written by
-    // calling f(arg)---is at least as current as the value we read from done.
-    //
-    // In version control terms, this is a lot like saying "sync up to the
-    // commit where we wrote done = true".
-    //
-    // The release barrier in sk_once_slow guaranteed that done = true
-    // happens after f(arg), so by syncing to done = true here we're
-    // forcing ourselves to also wait until the effects of f(arg) are readble.
-    SkAssertResult(sk_acquire_load(done));
 }
 
 template <typename Arg>
 inline void SkOnce(SkOnceFlag* once, void (*f)(Arg), Arg arg) {
     return SkOnce(once->mutableDone(), once, f, arg);
 }
 
 // Calls its argument.
 // This lets us use functions that take no arguments with SkOnce methods above.
 // (We pass _this_ as the function and the no-arg function as its argument.  Cute eh?)
 static void sk_once_no_arg_adaptor(void (*f)()) {
     f();
 }
 
 inline void SkOnce(SkOnceFlag* once, void (*func)()) {
     return SkOnce(once, sk_once_no_arg_adaptor, func);
 }
 
 template <typename Lock>
 inline void SkOnce(bool* done, Lock* lock, void (*func)()) {
     return SkOnce(done, lock, sk_once_no_arg_adaptor, func);
 }
 
 #endif  // SkOnce_DEFINED