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POSynchronise 3 threads with 3 condition variables
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copied!<p>I'm writing a program in c++ in a vtk/QT environment. This problem, however, is mostly a question of approach/algorithm.</p> <p>I am stuck in an attempt to synchronise my three running threads: 1. thread: transmit one sample at a time, and adds it to a "output" buffer 2. thread: receives one sample at a time, and adds it to a "input" buffer 3. thread: pulls data from "output" and "input" buffers and ads them to separate plotting buffers, for rendering.</p> <p>I want these threads to be run synchronised, and have there-for tried an approach where I use one condition variable together with a boolian condition for each of the threads, where one thread signals to the next and so fourth in a loop, in the order listed above. However, when I do this I get a deadlock and my program stops. I would really appreciate some input here:)</p> <p>Here's my approach in code:</p> <p>//Initialcondition for the boolian variables:</p> <pre><code>readyForTransmit=true; readyForReceive=false; readyForPlotting=false; </code></pre> <p>Thread 1 - transmit:</p> <pre><code>while(1){ mutex->Lock(); //waits for condition/signal to proceed while(!readyForTransmit) transmitConditionVariable->wait(mutex); readyForTransmit=false; mutex->Unlock(); //Here I transmit my sample transmit(); //Triggers next thread - reception mutex->Lock(); readyForReceive=true; receiveConditionVariable->broadcast(); //Have also tried signal(); mutex->Unlock(); } </code></pre> <p>Thread 2 - receive:</p> <pre><code>while(1){ mutex->Lock(); //waits for condition/signal to proceed while(!readyForReceive) receiveConditionVariable->wait(mutex); readyForReceive=false; mutex->Unlock(); //Here I receive my sample receive(); //Triggers next thread - reception mutex->Lock(); readyForPlotting=true; plottingConditionVariable->broadcast(); //Have also tried signal(); mutex->Unlock(); } </code></pre> <p>Thread 3 - adds to plotting buffers:</p> <pre><code>while(1){ mutex->Lock(); //waits for condition/signal to proceed while(!readyForPlotting) plottingConditionVariable->wait(mutex); readyForPlotting=false; mutex->Unlock(); //Here I adds samples to plotting buffer updatePlottingBuffers(); //Triggers next thread - reception mutex->Lock(); readyForTransmit=true; transmitConditionVariable->broadcast(); //Have also tried signal(); mutex->Unlock(); } </code></pre> <p>In addition to this I push and pull samples thread-safe to and from the buffers. So that shouldn't be a problem.</p> <p>Hope to hear from you! =)</p>

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