Class: ConditionVariable

Inherits:
Object
  • Object
show all
Defined in:
lib/thread.rb,
thread.c,
thread.c

Overview

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:

require 'thread'

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
  }
}

Instance Method Summary collapse

Constructor Details

#initialize ⇒ ConditionVariable

Creates a new ConditionVariable



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# File 'lib/thread.rb', line 187

def initialize
  @waiters = []
end

Instance Method Details

#broadcast ⇒ Object

Wakes up all threads waiting for this condition.



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# File 'lib/thread.rb', line 220

def broadcast
  waiters0 = nil
  Thread.exclusive do
    waiters0 = @waiters.dup
    @waiters.clear
  end
  for t in waiters0
    begin
	t.run
    rescue ThreadError
    end
  end
end

#marshal_dump ⇒ Object 



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# File 'thread.c', line 1124

static VALUE
dummy_dump(VALUE self)
{
    return rb_str_new2("");
}

#marshal_load(string) ⇒ Object

for marshalling mutexes and condvars



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# File 'thread.c', line 1118

static VALUE
dummy_load(VALUE self, VALUE string)
{
    return Qnil;
}

#signal ⇒ Object

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



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# File 'lib/thread.rb', line 208

def signal
  begin
    t = @waiters.shift
    t.run if t
  rescue ThreadError
    retry
  end
end

#wait ⇒ Object

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



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# File 'lib/thread.rb', line 194

def wait(mutex)
  begin
    mutex.exclusive_unlock do
      @waiters.push(Thread.current)
      Thread.stop
    end
  ensure
    mutex.lock
  end
end