84     mutex_ = new Mutex;  in this()
85     condition_ = new Condition(mutex_);  in this()
89     synchronized (mutex_) {  in wait()
95     synchronized (mutex_) {  in wait()
103     mutex_.lock();  in addCallback()
104     scope (failure) mutex_.unlock();  in addCallback()
109       mutex_.unlock();  in addCallback()
114     mutex_.unlock();  in addCallback()
118     synchronized (mutex_) {  in removeCallback()
132     synchronized (mutex_) {  in trigger()
143   Mutex mutex_;  variable