fix: address mutex deadlock in state machine #627
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corneliusclaussen
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Apr 12, 2024
There was a deadlock in the IEC state machine when the C1 timer expires whilst the state machine is running and attempting to stop the timer. The timer riases an event (hence blocks on the mutex) Stopping the timer waits for the thread to finish. Since the state machine is holding the mutex the thread never finishes ... fix: improvement to EventQueue Wait on the condition variable now checks the queue size to avoid spurious wakeups. https://en.cppreference.com/w/cpp/thread/condition_variable Signed-off-by: James Chapman <[email protected]>
Signed-off-by: James Chapman <[email protected]>
Signed-off-by: James Chapman <[email protected]>
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The IEC state machine uses threads to decouple events from the state machine, hence events don't always arrive in the expected order which causes some tests to occasionally fail. Signed-off-by: James Chapman <[email protected]>
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There was a deadlock in the IEC state machine when the C1 timer expires whilst the state machine is running and attempting to stop the timer.
The timer raises an event (hence blocks on the mutex) Stopping the timer waits for the thread to finish. Since the state machine is holding the mutex the thread never finishes ...
fix: improvement to EventQueue
Wait on the condition variable now checks the queue size to avoid spurious wakeups.
https://en.cppreference.com/w/cpp/thread/condition_variable
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