1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "base/at_exit.h"
6
7 #include <stddef.h>
8 #include <ostream>
9 #include <utility>
10
11 #include "base/bind.h"
12 #include "base/callback.h"
13 #include "base/logging.h"
14
15 namespace base {
16
17 // Keep a stack of registered AtExitManagers. We always operate on the most
18 // recent, and we should never have more than one outside of testing (for a
19 // statically linked version of this library). Testing may use the shadow
20 // version of the constructor, and if we are building a dynamic library we may
21 // end up with multiple AtExitManagers on the same process. We don't protect
22 // this for thread-safe access, since it will only be modified in testing.
23 static AtExitManager* g_top_manager = NULL;
24
AtExitManager()25 AtExitManager::AtExitManager()
26 : processing_callbacks_(false), next_manager_(g_top_manager) {
27 // If multiple modules instantiate AtExitManagers they'll end up living in this
28 // module... they have to coexist.
29 #if !defined(COMPONENT_BUILD)
30 DCHECK(!g_top_manager);
31 #endif
32 g_top_manager = this;
33 }
34
~AtExitManager()35 AtExitManager::~AtExitManager() {
36 if (!g_top_manager) {
37 NOTREACHED() << "Tried to ~AtExitManager without an AtExitManager";
38 return;
39 }
40 DCHECK_EQ(this, g_top_manager);
41
42 ProcessCallbacksNow();
43 g_top_manager = next_manager_;
44 }
45
46 // static
RegisterCallback(AtExitCallbackType func,void * param)47 void AtExitManager::RegisterCallback(AtExitCallbackType func, void* param) {
48 DCHECK(func);
49 RegisterTask(base::Bind(func, param));
50 }
51
52 // static
RegisterTask(base::Closure task)53 void AtExitManager::RegisterTask(base::Closure task) {
54 if (!g_top_manager) {
55 NOTREACHED() << "Tried to RegisterCallback without an AtExitManager";
56 return;
57 }
58
59 AutoLock lock(g_top_manager->lock_);
60 DCHECK(!g_top_manager->processing_callbacks_);
61 g_top_manager->stack_.push(std::move(task));
62 }
63
64 // static
ProcessCallbacksNow()65 void AtExitManager::ProcessCallbacksNow() {
66 if (!g_top_manager) {
67 NOTREACHED() << "Tried to ProcessCallbacksNow without an AtExitManager";
68 return;
69 }
70
71 // Callbacks may try to add new callbacks, so run them without holding
72 // |lock_|. This is an error and caught by the DCHECK in RegisterTask(), but
73 // handle it gracefully in release builds so we don't deadlock.
74 std::stack<base::Closure> tasks;
75 {
76 AutoLock lock(g_top_manager->lock_);
77 tasks.swap(g_top_manager->stack_);
78 g_top_manager->processing_callbacks_ = true;
79 }
80
81 while (!tasks.empty()) {
82 base::Closure task = tasks.top();
83 task.Run();
84 tasks.pop();
85 }
86
87 // Expect that all callbacks have been run.
88 DCHECK(g_top_manager->stack_.empty());
89 }
90
AtExitManager(bool shadow)91 AtExitManager::AtExitManager(bool shadow)
92 : processing_callbacks_(false), next_manager_(g_top_manager) {
93 DCHECK(shadow || !g_top_manager);
94 g_top_manager = this;
95 }
96
97 } // namespace base
98