ConditionVariable

Class

ConditionVariable objects augment class Mutex. Using condition variables, it is possible to suspend while in the middle of a critical section until a resource becomes available.

Example:

mutex = Mutex.new
resource = ConditionVariable.new

a = Thread.new {
   mutex.synchronize {
     # Thread 'a' now needs the resource
     resource.wait(mutex)
     # 'a' can now have the resource
   }
}

b = Thread.new {
   mutex.synchronize {
     # Thread 'b' has finished using the resource
     resource.signal
   }
}

Class Methods

new

thread_sync.c View on GitHub

          
            static VALUE
rb_condvar_initialize(VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);;
    list_head_init(&cv->waitq);
    return self;
}

Creates a new condition variable instance.

Instance Methods

broadcast

thread_sync.c View on GitHub

          
            static VALUE
rb_condvar_broadcast(VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_all(&cv->waitq);
    return self;
}

Wakes up all threads waiting for this lock.

signal

thread_sync.c View on GitHub

          
            static VALUE
rb_condvar_signal(VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_one(&cv->waitq);
    return self;
}

Wakes up the first thread in line waiting for this lock.

wait(mutex, timeout=nil)

thread_sync.c View on GitHub

          
            static VALUE
rb_condvar_wait(int argc, VALUE *argv, VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    VALUE mutex, timeout;
    struct sleep_call args;
    struct sync_waiter w;

    rb_scan_args(argc, argv, "11", &mutex, &timeout);

    args.mutex   = mutex;
    args.timeout = timeout;
    w.th = GET_THREAD();
    list_add_tail(&cv->waitq, &w.node);
    rb_ensure(do_sleep, (VALUE)&args, delete_from_waitq, (VALUE)&w);

    return self;
}

Releases the lock held in mutex and waits; reacquires the lock on wakeup.

If timeout is given, this method returns after timeout seconds passed, even if no other thread doesn’t signal.