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// Copyright 2011 The Chromium Authors
// 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/check_op.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/notreached.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
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