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require File.dirname(__FILE__) + '/../../spec_helper'
require 'thread'
describe "ConditionVariable#signal" do
it "should return self if nothing to signal" do
cv = ConditionVariable.new
cv.signal.should == cv
end
it "should return self if something is waiting for a signal" do
m = Mutex.new
cv = ConditionVariable.new
th = Thread.new do
m.synchronize do
cv.wait(m)
end
end
# ensures that th grabs m before current thread
Thread.pass until th.status == "sleep"
m.synchronize { cv.signal }.should == cv
th.join
end
it "releases the first thread waiting in line for this resource" do
m = Mutex.new
cv = ConditionVariable.new
threads = []
r1 = []
r2 = []
# large number to attempt to cause race conditions
100.times do |i|
threads << Thread.new(i) do |tid|
m.synchronize do
r1 << tid
cv.wait(m)
r2 << tid
end
end
end
# wait for all threads to acquire the mutex the first time
Thread.pass until m.synchronize { r1.size == threads.size }
# wait until all threads are sleeping (ie waiting)
Thread.pass until threads.all? {|th| th.status == "sleep" }
r2.should be_empty
100.times do |i|
m.synchronize do
cv.signal
end
Thread.pass until r2.size == i+1
end
threads.each {|t| t.join }
# ensure that all the threads that went into the cv.wait are
# released in the same order
r2.should == r1
end
end
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