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require_relative '../../spec_helper'
require 'thread'
describe "ConditionVariable#signal" do
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?(&:stop?)
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
it "allows control to be passed between a pair of threads" do
m = Mutex.new
cv = ConditionVariable.new
repeats = 100
in_synchronize = false
t1 = Thread.new do
m.synchronize do
in_synchronize = true
repeats.times do
cv.wait(m)
cv.signal
end
end
end
# Make sure t1 is waiting for a signal before launching t2.
Thread.pass until in_synchronize
Thread.pass until t1.stop?
t2 = Thread.new do
m.synchronize do
repeats.times do
cv.signal
cv.wait(m)
end
end
end
# Check that both threads terminated without exception
t1.join
t2.join
m.should_not.locked?
end
end
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