Ben Murdoch | b8a8cc1 | 2014-11-26 15:28:44 +0000 | [diff] [blame^] | 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_CONDITION_VARIABLE_H_ |
| 6 | #define V8_BASE_PLATFORM_CONDITION_VARIABLE_H_ |
| 7 | |
| 8 | #include "src/base/lazy-instance.h" |
| 9 | #include "src/base/platform/mutex.h" |
| 10 | |
| 11 | namespace v8 { |
| 12 | namespace base { |
| 13 | |
| 14 | // Forward declarations. |
| 15 | class ConditionVariableEvent; |
| 16 | class TimeDelta; |
| 17 | |
| 18 | // ----------------------------------------------------------------------------- |
| 19 | // ConditionVariable |
| 20 | // |
| 21 | // This class is a synchronization primitive that can be used to block a thread, |
| 22 | // or multiple threads at the same time, until: |
| 23 | // - a notification is received from another thread, |
| 24 | // - a timeout expires, or |
| 25 | // - a spurious wakeup occurs |
| 26 | // Any thread that intends to wait on a ConditionVariable has to acquire a lock |
| 27 | // on a Mutex first. The |Wait()| and |WaitFor()| operations atomically release |
| 28 | // the mutex and suspend the execution of the calling thread. When the condition |
| 29 | // variable is notified, the thread is awakened, and the mutex is reacquired. |
| 30 | |
| 31 | class ConditionVariable FINAL { |
| 32 | public: |
| 33 | ConditionVariable(); |
| 34 | ~ConditionVariable(); |
| 35 | |
| 36 | // If any threads are waiting on this condition variable, calling |
| 37 | // |NotifyOne()| unblocks one of the waiting threads. |
| 38 | void NotifyOne(); |
| 39 | |
| 40 | // Unblocks all threads currently waiting for this condition variable. |
| 41 | void NotifyAll(); |
| 42 | |
| 43 | // |Wait()| causes the calling thread to block until the condition variable is |
| 44 | // notified or a spurious wakeup occurs. Atomically releases the mutex, blocks |
| 45 | // the current executing thread, and adds it to the list of threads waiting on |
| 46 | // this condition variable. The thread will be unblocked when |NotifyAll()| or |
| 47 | // |NotifyOne()| is executed. It may also be unblocked spuriously. When |
| 48 | // unblocked, regardless of the reason, the lock on the mutex is reacquired |
| 49 | // and |Wait()| exits. |
| 50 | void Wait(Mutex* mutex); |
| 51 | |
| 52 | // Atomically releases the mutex, blocks the current executing thread, and |
| 53 | // adds it to the list of threads waiting on this condition variable. The |
| 54 | // thread will be unblocked when |NotifyAll()| or |NotifyOne()| is executed, |
| 55 | // or when the relative timeout |rel_time| expires. It may also be unblocked |
| 56 | // spuriously. When unblocked, regardless of the reason, the lock on the mutex |
| 57 | // is reacquired and |WaitFor()| exits. Returns true if the condition variable |
| 58 | // was notified prior to the timeout. |
| 59 | bool WaitFor(Mutex* mutex, const TimeDelta& rel_time) WARN_UNUSED_RESULT; |
| 60 | |
| 61 | // The implementation-defined native handle type. |
| 62 | #if V8_OS_POSIX |
| 63 | typedef pthread_cond_t NativeHandle; |
| 64 | #elif V8_OS_WIN |
| 65 | struct Event; |
| 66 | class NativeHandle FINAL { |
| 67 | public: |
| 68 | NativeHandle() : waitlist_(NULL), freelist_(NULL) {} |
| 69 | ~NativeHandle(); |
| 70 | |
| 71 | Event* Pre() WARN_UNUSED_RESULT; |
| 72 | void Post(Event* event, bool result); |
| 73 | |
| 74 | Mutex* mutex() { return &mutex_; } |
| 75 | Event* waitlist() { return waitlist_; } |
| 76 | |
| 77 | private: |
| 78 | Event* waitlist_; |
| 79 | Event* freelist_; |
| 80 | Mutex mutex_; |
| 81 | |
| 82 | DISALLOW_COPY_AND_ASSIGN(NativeHandle); |
| 83 | }; |
| 84 | #endif |
| 85 | |
| 86 | NativeHandle& native_handle() { |
| 87 | return native_handle_; |
| 88 | } |
| 89 | const NativeHandle& native_handle() const { |
| 90 | return native_handle_; |
| 91 | } |
| 92 | |
| 93 | private: |
| 94 | NativeHandle native_handle_; |
| 95 | |
| 96 | DISALLOW_COPY_AND_ASSIGN(ConditionVariable); |
| 97 | }; |
| 98 | |
| 99 | |
| 100 | // POD ConditionVariable initialized lazily (i.e. the first time Pointer() is |
| 101 | // called). |
| 102 | // Usage: |
| 103 | // static LazyConditionVariable my_condvar = |
| 104 | // LAZY_CONDITION_VARIABLE_INITIALIZER; |
| 105 | // |
| 106 | // void my_function() { |
| 107 | // LockGuard<Mutex> lock_guard(&my_mutex); |
| 108 | // my_condvar.Pointer()->Wait(&my_mutex); |
| 109 | // } |
| 110 | typedef LazyStaticInstance< |
| 111 | ConditionVariable, DefaultConstructTrait<ConditionVariable>, |
| 112 | ThreadSafeInitOnceTrait>::type LazyConditionVariable; |
| 113 | |
| 114 | #define LAZY_CONDITION_VARIABLE_INITIALIZER LAZY_STATIC_INSTANCE_INITIALIZER |
| 115 | |
| 116 | } } // namespace v8::base |
| 117 | |
| 118 | #endif // V8_BASE_PLATFORM_CONDITION_VARIABLE_H_ |