Make leak counters thread-safe

src/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
-
-// 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.  This
-// is particularly useful for lazy singleton initialization. E.g.
-//
-// static void set_up_my_singleton(Singleton** singleton) {
-//     *singleton = new Singleton(...);
-// }
-// ...
-// const Singleton& GetSingleton() {
-//     static Singleton* singleton = NULL;
-//     SK_DECLARE_STATIC_ONCE(once);
-//     SkOnce(&once, set_up_my_singleton, &singleton);
-//     SkASSERT(NULL != singleton);
-//     return *singleton;
-// }
-//
-// OnceTest.cpp also should serve as a few other simple examples.
-
-#include "SkThread.h"
-#include "SkTypes.h"
-
-#define SK_ONCE_INIT { false, { 0, SkDEBUGCODE(0) } }
-#define SK_DECLARE_STATIC_ONCE(name) static SkOnceFlag name = SK_ONCE_INIT
-
-struct SkOnceFlag;  // If manually created, initialize with SkOnceFlag once = SK_ONCE_INIT
-
-template <typename Func, typename Arg>
-inline void SkOnce(SkOnceFlag* once, Func f, Arg arg);
-
-//  ----------------------  Implementation details below here. -----------------------------
-
-struct SkOnceFlag {
-    bool done;
-    SkSpinlock lock;
-};
-
-// TODO(bungeman, mtklein): move all these *barrier* functions to SkThread when refactoring lands.
-
-#ifdef SK_BUILD_FOR_WIN
-#  include <intrin.h>
-inline static void compiler_barrier() {
-    _ReadWriteBarrier();
-}
-#else
-inline static void compiler_barrier() {
-    asm volatile("" : : : "memory");
-}
-#endif
-
-inline static void full_barrier_on_arm() {
-#ifdef SK_CPU_ARM
-#  if SK_ARM_ARCH >= 7
-    asm volatile("dmb" : : : "memory");
-#  else
-    asm volatile("mcr p15, 0, %0, c7, c10, 5" : : "r" (0) : "memory");
-#  endif
-#endif
-}
-
-// On every platform, we issue a compiler barrier to prevent it from reordering
-// code.  That's enough for platforms like x86 where release and acquire
-// barriers are no-ops.  On other platforms we may need to be more careful;
-// ARM, in particular, needs real code for both acquire and release.  We use a
-// full barrier, which acts as both, because that the finest precision ARM
-// provides.
-
-inline static void release_barrier() {
-    compiler_barrier();
-    full_barrier_on_arm();
-}
-
-inline static void acquire_barrier() {
-    compiler_barrier();
-    full_barrier_on_arm();
-}
-
-// 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 Func, typename Arg>
-static void sk_once_slow(SkOnceFlag* once, Func f, Arg arg) {
-    const SkAutoSpinlock lock(&once->lock);
-    if (!once->done) {
-        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.
-        release_barrier();
-        once->done = true;
-    }
-}
-
-// We nabbed this code from the dynamic_annotations library, and in their honor
-// we check the same define.  If you find yourself wanting more than just
-// ANNOTATE_BENIGN_RACE, it might make sense to pull that in as a dependency
-// rather than continue to reproduce it here.
-
-#if DYNAMIC_ANNOTATIONS_ENABLED
-// TSAN provides this hook to supress a known-safe apparent race.
-extern "C" {
-void AnnotateBenignRace(const char* file, int line, const volatile void* mem, const char* desc);
-}
-#define ANNOTATE_BENIGN_RACE(mem, desc) AnnotateBenignRace(__FILE__, __LINE__, mem, desc)
-#else
-#define ANNOTATE_BENIGN_RACE(mem, desc)
-#endif
-
-// This is our fast path, called all the time.  We do really want it to be inlined.
-template <typename Func, typename Arg>
-inline void SkOnce(SkOnceFlag* once, Func f, Arg arg) {
-    ANNOTATE_BENIGN_RACE(&(once->done), "Don't worry TSAN, we're sure this is safe.");
-    if (!once->done) {
-        sk_once_slow(once, 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 once->done.
-    //
-    // In version control terms, this is a lot like saying "sync up to the
-    // commit where we wrote once->done = true".
-    //
-    // The release barrier in sk_once_slow guaranteed that once->done = true
-    // happens after f(arg), so by syncing to once->done = true here we're
-    // forcing ourselves to also wait until the effects of f(arg) are readble.
-    acquire_barrier();
-}
-
-#undef ANNOTATE_BENIGN_RACE
-
-#endif  // SkOnce_DEFINED