Repo created

TMessagesProj/jni/voip/webrtc/base/at_exit.cc

@@ -0,0 +1,114 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/at_exit.h"
+
+#include <stddef.h>
+#include <ostream>
+#include <utility>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/logging.h"
+
+namespace base {
+
+// Keep a stack of registered AtExitManagers.  We always operate on the most
+// recent, and we should never have more than one outside of testing (for a
+// statically linked version of this library).  Testing may use the shadow
+// version of the constructor, and if we are building a dynamic library we may
+// end up with multiple AtExitManagers on the same process.  We don't protect
+// this for thread-safe access, since it will only be modified in testing.
+static AtExitManager* g_top_manager = nullptr;
+
+static bool g_disable_managers = false;
+
+AtExitManager::AtExitManager() : next_manager_(g_top_manager) {
+// If multiple modules instantiate AtExitManagers they'll end up living in this
+// module... they have to coexist.
+#if !defined(COMPONENT_BUILD)
+  DCHECK(!g_top_manager);
+#endif
+  g_top_manager = this;
+}
+
+AtExitManager::~AtExitManager() {
+  if (!g_top_manager) {
+    NOTREACHED() << "Tried to ~AtExitManager without an AtExitManager";
+    return;
+  }
+  DCHECK_EQ(this, g_top_manager);
+
+  if (!g_disable_managers)
+    ProcessCallbacksNow();
+  g_top_manager = next_manager_;
+}
+
+// static
+void AtExitManager::RegisterCallback(AtExitCallbackType func, void* param) {
+  DCHECK(func);
+  RegisterTask(base::BindOnce(func, param));
+}
+
+// static
+void AtExitManager::RegisterTask(base::OnceClosure task) {
+  if (!g_top_manager) {
+    NOTREACHED() << "Tried to RegisterCallback without an AtExitManager";
+    return;
+  }
+
+  AutoLock lock(g_top_manager->lock_);
+#if DCHECK_IS_ON()
+  DCHECK(!g_top_manager->processing_callbacks_);
+#endif
+  g_top_manager->stack_.push(std::move(task));
+}
+
+// static
+void AtExitManager::ProcessCallbacksNow() {
+  if (!g_top_manager) {
+    NOTREACHED() << "Tried to ProcessCallbacksNow without an AtExitManager";
+    return;
+  }
+
+  // Callbacks may try to add new callbacks, so run them without holding
+  // |lock_|. This is an error and caught by the DCHECK in RegisterTask(), but
+  // handle it gracefully in release builds so we don't deadlock.
+  base::stack<base::OnceClosure> tasks;
+  {
+    AutoLock lock(g_top_manager->lock_);
+    tasks.swap(g_top_manager->stack_);
+#if DCHECK_IS_ON()
+    g_top_manager->processing_callbacks_ = true;
+#endif
+  }
+
+  // Relax the cross-thread access restriction to non-thread-safe RefCount.
+  // It's safe since all other threads should be terminated at this point.
+  ScopedAllowCrossThreadRefCountAccess allow_cross_thread_ref_count_access;
+
+  while (!tasks.empty()) {
+    std::move(tasks.top()).Run();
+    tasks.pop();
+  }
+
+#if DCHECK_IS_ON()
+  AutoLock lock(g_top_manager->lock_);
+  // Expect that all callbacks have been run.
+  DCHECK(g_top_manager->stack_.empty());
+  g_top_manager->processing_callbacks_ = false;
+#endif
+}
+
+void AtExitManager::DisableAllAtExitManagers() {
+  AutoLock lock(g_top_manager->lock_);
+  g_disable_managers = true;
+}
+
+AtExitManager::AtExitManager(bool shadow) : next_manager_(g_top_manager) {
+  DCHECK(shadow || !g_top_manager);
+  g_top_manager = this;
+}
+
+}  // namespace base