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  • thread_sync.c

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ConditionVariable

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
   }
}

Public Class Methods

new() click to toggle source

Creates a new condition variable instance.

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

Public Instance Methods

broadcast() click to toggle source

Wakes up all threads waiting for this lock.

 
               static VALUE
rb_condvar_broadcast(VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_all(&cv->waitq);
    return self;
}
            
marshal_dump() click to toggle source
 
               static VALUE undumpable(VALUE obj))
            
signal() click to toggle source

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

 
               static VALUE
rb_condvar_signal(VALUE self)
{
    struct rb_condvar *cv = condvar_ptr(self);
    wakeup_one(&cv->waitq);
    return self;
}
            
wait(mutex, timeout=nil) click to toggle source

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.

 
               static VALUE
rb_condvar_wait(int argc, VALUE *argv, VALUE self)
{
    rb_execution_context_t *ec = GET_EC();

    struct rb_condvar *cv = condvar_ptr(self);
    struct sleep_call args;

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

    struct sync_waiter w = {
        .self = args.mutex,
        .th = ec->thread_ptr,
        .fiber = ec->fiber_ptr,
    };

    list_add_tail(&cv->waitq, &w.node);
    rb_ensure(do_sleep, (VALUE)&args, delete_from_waitq, (VALUE)&w);

    return self;
}