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Added more robust shutdown code for our dmJobThread implementation #8762

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merged 1 commit into from Apr 6, 2024
Merged

Added more robust shutdown code for our dmJobThread implementation #8762

merged 1 commit into from Apr 6, 2024

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JCash
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@JCash JCash commented Apr 5, 2024

This fixes an issue where it was possible for get a dead lock when shutting down the job thread system.

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There was a anomaly in the carbon chroniton propeller, introduced in version 8.10.2. This fix will make sure to reset the phaser collector on application startup.

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* Pay special attention to line 23 of phaser_collector.clj as it contains some interesting optimizations
* The propeller code was not taking into account a negative phase.

@JCash JCash requested a review from Jhonnyg April 5, 2024 11:48
JCash
JCash commented Apr 5, 2024
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engine/dlib/src/dlib/job_thread.cpp
@@ -53,7 +53,7 @@ struct JobThreadContext
#if defined(DM_HAS_THREADS)
dmMutex::HMutex m_Mutex;
dmConditionVariable::HConditionVariable m_WakeupCond;
int32_atomic_t m_Run;
bool m_Run;
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No need for atomics if we already use a mutex.

engine/dlib/src/dlib/job_thread.cpp
Comment on lines +92 to +94
while (true)
{
JobItem item;
JobItem item = {};
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Between the loop check and the dmConditionVariable::Wait(), the main thread set run=0 and also signalled the wakeup condition...

engine/dlib/src/dlib/job_thread.cpp

if (!ctx->m_Run)
break;

while(ctx->m_Work.Empty())
{
dmConditionVariable::Wait(ctx->m_WakeupCond, ctx->m_Mutex);
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Once we got here, the signal had already been sent which meant that the wait would then stall forever, as there wouldn't be any new signal coming.

engine/dlib/src/dlib/job_thread.cpp

context->m_ThreadContext.m_Run = false;;

dmConditionVariable::Broadcast(context->m_ThreadContext.m_WakeupCond);
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Better to wakeup all threads at once.

engine/dlib/src/dlib/job_thread.cpp
dmConditionVariable::Signal(context->m_ThreadContext.m_WakeupCond);
}

context->m_ThreadContext.m_Run = false;;
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Now we know that the Run and Wait() are within the same protected scope on the thread and here as well.

Jhonnyg
Jhonnyg approved these changes Apr 5, 2024
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Lgtm but there’s no tests, do we want that perhaps?

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JCash commented Apr 6, 2024

I'd say yes, but I'm not sure how to write such a test that actually catches/tests the issue in a 100% manner?

@JCash JCash merged commit 6a5fc39 into dev Apr 6, 2024
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@JCash JCash deleted the job-thread-shutdown-fix branch April 6, 2024 14:30
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@Jhonnyg Jhonnyg Jhonnyg approved these changes

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