Pages 136-7: Mutual exclusion - Monitors (part II)

Value: Average

Level: Easy

Summary:
You can include MonitorMixin instead of using Monitor as a superclass. If all accesses to all objects of the class require synchronization, you'll put synchronization inside the resource being synchronized (see previous post). Otherwise you can use an external monitor.

Memo: While external monitors are safe, try to avoid making specific objects into monitors.

Example:
require 'monitor'
class Counter
    attr_reader :count
    def initialize
        @count = 0
    end
    def tick
        @count += 1
    end
end
c = Counter.new
lock = Monitor.new
t1 = Thread.new { 10000.times { lock.synchronize { c.tick } } }
t2 = Thread.new { 10000.times { lock.synchronize { c.tick } } }
t1.join; t2.join
c.count

Reported errata (at 10/17/06 14:17:18 PDT): 0

Errata I found: 0

My suggestions to the author: 0

Doubts: 0