class Thread::ConditionVariable - Documentation for Ruby 3.3

# class Thread::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 = Thread::Mutex.new
    resource = Thread::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);
        ccan_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;
    }

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.

Returns the slept result on `mutex`.

    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 sync_waiter = {
            .self = args.mutex,
            .th = ec->thread_ptr,
            .fiber = nonblocking_fiber(ec->fiber_ptr)
        };

        ccan_list_add_tail(&cv->waitq, &sync_waiter.node);
        return rb_ensure(do_sleep, (VALUE)&args, delete_from_waitq, (VALUE)&sync_waiter);
    }