Line data Source code
1 : // Copyright 2013 the V8 project 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 : #ifndef V8_BASE_PLATFORM_MUTEX_H_
6 : #define V8_BASE_PLATFORM_MUTEX_H_
7 :
8 : #include "src/base/base-export.h"
9 : #include "src/base/lazy-instance.h"
10 : #if V8_OS_WIN
11 : #include "src/base/win32-headers.h"
12 : #endif
13 : #include "src/base/logging.h"
14 :
15 : #if V8_OS_POSIX
16 : #include <pthread.h> // NOLINT
17 : #endif
18 :
19 : namespace v8 {
20 : namespace base {
21 :
22 : // ----------------------------------------------------------------------------
23 : // Mutex
24 : //
25 : // This class is a synchronization primitive that can be used to protect shared
26 : // data from being simultaneously accessed by multiple threads. A mutex offers
27 : // exclusive, non-recursive ownership semantics:
28 : // - A calling thread owns a mutex from the time that it successfully calls
29 : // either |Lock()| or |TryLock()| until it calls |Unlock()|.
30 : // - When a thread owns a mutex, all other threads will block (for calls to
31 : // |Lock()|) or receive a |false| return value (for |TryLock()|) if they
32 : // attempt to claim ownership of the mutex.
33 : // A calling thread must not own the mutex prior to calling |Lock()| or
34 : // |TryLock()|. The behavior of a program is undefined if a mutex is destroyed
35 : // while still owned by some thread. The Mutex class is non-copyable.
36 :
37 : class V8_BASE_EXPORT Mutex final {
38 : public:
39 : Mutex();
40 : ~Mutex();
41 :
42 : // Locks the given mutex. If the mutex is currently unlocked, it becomes
43 : // locked and owned by the calling thread, and immediately. If the mutex
44 : // is already locked by another thread, suspends the calling thread until
45 : // the mutex is unlocked.
46 : void Lock();
47 :
48 : // Unlocks the given mutex. The mutex is assumed to be locked and owned by
49 : // the calling thread on entrance.
50 : void Unlock();
51 :
52 : // Tries to lock the given mutex. Returns whether the mutex was
53 : // successfully locked.
54 : bool TryLock() V8_WARN_UNUSED_RESULT;
55 :
56 : // The implementation-defined native handle type.
57 : #if V8_OS_POSIX
58 : typedef pthread_mutex_t NativeHandle;
59 : #elif V8_OS_WIN
60 : typedef SRWLOCK NativeHandle;
61 : #endif
62 :
63 : NativeHandle& native_handle() {
64 : return native_handle_;
65 : }
66 : const NativeHandle& native_handle() const {
67 : return native_handle_;
68 : }
69 :
70 : private:
71 : NativeHandle native_handle_;
72 : #ifdef DEBUG
73 : int level_;
74 : #endif
75 :
76 : V8_INLINE void AssertHeldAndUnmark() {
77 : #ifdef DEBUG
78 : DCHECK_EQ(1, level_);
79 : level_--;
80 : #endif
81 : }
82 :
83 : V8_INLINE void AssertUnheldAndMark() {
84 : #ifdef DEBUG
85 : DCHECK_EQ(0, level_);
86 : level_++;
87 : #endif
88 : }
89 :
90 : friend class ConditionVariable;
91 :
92 : DISALLOW_COPY_AND_ASSIGN(Mutex);
93 : };
94 :
95 : // POD Mutex initialized lazily (i.e. the first time Pointer() is called).
96 : // Usage:
97 : // static LazyMutex my_mutex = LAZY_MUTEX_INITIALIZER;
98 : //
99 : // void my_function() {
100 : // MutexGuard guard(my_mutex.Pointer());
101 : // // Do something.
102 : // }
103 : //
104 : typedef LazyStaticInstance<Mutex, DefaultConstructTrait<Mutex>,
105 : ThreadSafeInitOnceTrait>::type LazyMutex;
106 :
107 : #define LAZY_MUTEX_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER
108 :
109 :
110 : // -----------------------------------------------------------------------------
111 : // RecursiveMutex
112 : //
113 : // This class is a synchronization primitive that can be used to protect shared
114 : // data from being simultaneously accessed by multiple threads. A recursive
115 : // mutex offers exclusive, recursive ownership semantics:
116 : // - A calling thread owns a recursive mutex for a period of time that starts
117 : // when it successfully calls either |Lock()| or |TryLock()|. During this
118 : // period, the thread may make additional calls to |Lock()| or |TryLock()|.
119 : // The period of ownership ends when the thread makes a matching number of
120 : // calls to |Unlock()|.
121 : // - When a thread owns a recursive mutex, all other threads will block (for
122 : // calls to |Lock()|) or receive a |false| return value (for |TryLock()|) if
123 : // they attempt to claim ownership of the recursive mutex.
124 : // - The maximum number of times that a recursive mutex may be locked is
125 : // unspecified, but after that number is reached, calls to |Lock()| will
126 : // probably abort the process and calls to |TryLock()| return false.
127 : // The behavior of a program is undefined if a recursive mutex is destroyed
128 : // while still owned by some thread. The RecursiveMutex class is non-copyable.
129 :
130 : class V8_BASE_EXPORT RecursiveMutex final {
131 : public:
132 : RecursiveMutex();
133 : ~RecursiveMutex();
134 :
135 : // Locks the mutex. If another thread has already locked the mutex, a call to
136 : // |Lock()| will block execution until the lock is acquired. A thread may call
137 : // |Lock()| on a recursive mutex repeatedly. Ownership will only be released
138 : // after the thread makes a matching number of calls to |Unlock()|.
139 : // The behavior is undefined if the mutex is not unlocked before being
140 : // destroyed, i.e. some thread still owns it.
141 : void Lock();
142 :
143 : // Unlocks the mutex if its level of ownership is 1 (there was exactly one
144 : // more call to |Lock()| than there were calls to unlock() made by this
145 : // thread), reduces the level of ownership by 1 otherwise. The mutex must be
146 : // locked by the current thread of execution, otherwise, the behavior is
147 : // undefined.
148 : void Unlock();
149 :
150 : // Tries to lock the given mutex. Returns whether the mutex was
151 : // successfully locked.
152 : bool TryLock() V8_WARN_UNUSED_RESULT;
153 :
154 : // The implementation-defined native handle type.
155 : #if V8_OS_POSIX
156 : typedef pthread_mutex_t NativeHandle;
157 : #elif V8_OS_WIN
158 : typedef CRITICAL_SECTION NativeHandle;
159 : #endif
160 :
161 : NativeHandle& native_handle() {
162 : return native_handle_;
163 : }
164 : const NativeHandle& native_handle() const {
165 : return native_handle_;
166 : }
167 :
168 : private:
169 : NativeHandle native_handle_;
170 : #ifdef DEBUG
171 : int level_;
172 : #endif
173 :
174 : DISALLOW_COPY_AND_ASSIGN(RecursiveMutex);
175 : };
176 :
177 :
178 : // POD RecursiveMutex initialized lazily (i.e. the first time Pointer() is
179 : // called).
180 : // Usage:
181 : // static LazyRecursiveMutex my_mutex = LAZY_RECURSIVE_MUTEX_INITIALIZER;
182 : //
183 : // void my_function() {
184 : // LockGuard<RecursiveMutex> guard(my_mutex.Pointer());
185 : // // Do something.
186 : // }
187 : //
188 : typedef LazyStaticInstance<RecursiveMutex,
189 : DefaultConstructTrait<RecursiveMutex>,
190 : ThreadSafeInitOnceTrait>::type LazyRecursiveMutex;
191 :
192 : #define LAZY_RECURSIVE_MUTEX_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER
193 :
194 :
195 : // -----------------------------------------------------------------------------
196 : // LockGuard
197 : //
198 : // This class is a mutex wrapper that provides a convenient RAII-style mechanism
199 : // for owning a mutex for the duration of a scoped block.
200 : // When a LockGuard object is created, it attempts to take ownership of the
201 : // mutex it is given. When control leaves the scope in which the LockGuard
202 : // object was created, the LockGuard is destructed and the mutex is released.
203 : // The LockGuard class is non-copyable.
204 :
205 : // Controls whether a LockGuard always requires a valid Mutex or will just
206 : // ignore it if it's nullptr.
207 : enum class NullBehavior { kRequireNotNull, kIgnoreIfNull };
208 :
209 : template <typename Mutex, NullBehavior Behavior = NullBehavior::kRequireNotNull>
210 : class LockGuard final {
211 : public:
212 15548083 : explicit LockGuard(Mutex* mutex) : mutex_(mutex) {
213 : if (Behavior == NullBehavior::kRequireNotNull || mutex_ != nullptr) {
214 344155217 : mutex_->Lock();
215 : }
216 15137048 : }
217 15136561 : ~LockGuard() {
218 343829560 : if (mutex_ != nullptr) mutex_->Unlock();
219 15136494 : }
220 :
221 : private:
222 : Mutex* mutex_;
223 :
224 : DISALLOW_COPY_AND_ASSIGN(LockGuard);
225 : };
226 :
227 : using MutexGuard = LockGuard<Mutex>;
228 :
229 : } // namespace base
230 : } // namespace v8
231 :
232 : #endif // V8_BASE_PLATFORM_MUTEX_H_
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