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    <p>Ok, the problem seems to be in your ThreadPool#signal method. What may happen is:</p> <p>1 - All your worker are busy and you try to process a new job</p> <p>2 - line 90 gets a nil worker</p> <p>3 - a worker get freed and signals it, but the signal is lost as the ThreadPool is not waiting for it</p> <p>4 - you fall on line 95, waiting even though there is a free worker.</p> <p>The error here is that you can signal a free worker even when nobody is listening. This ThreadPool#signal method should be:</p> <pre><code>def signal @mutex.synchronize { @cv.signal } end </code></pre> <p>And the problem is the same in the Worker object. What might happen is:</p> <p>1 - The Worker just completed a job</p> <p>2 - It checks (line 17) if there is a job waiting: there isn't</p> <p>3 - The thread pool send a new job and signals it ... but the signal is lost</p> <p>4 - The worker wait for a signal, even though it is marked as busy</p> <p>You should put your initialize method as:</p> <pre><code>def initialize(callback) @mutex = Mutex.new @cv = ConditionVariable.new @callback = callback @mutex.synchronize {@running = true} @thread = Thread.new do @mutex.synchronize do while @running block = get_block if block @mutex.unlock block.call @mutex.lock reset_block # Signal the ThreadPool that this worker is ready for another job @callback.signal else # Wait for a new job @cv.wait(@mutex) end end end end end </code></pre> <p>Next, the Worker#get_block and Worker#reset_block methods should not be synchronized anymore. That way, you cannot have a block assigned to a worker between the test for a block and the wait for a signal.</p>
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    1. PODeadlock in ThreadPool
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    1. USPierreBdR
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      1. VTUpMod
    1. COI think that you're right! I'll test this right away, thanks!
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      1. USRoman
    2. COHmm.. now there's a deadlock when I'm waiting for threads to complete (e.g. calling join for the ThreadPool). I'm trying to figure out why.
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