Nullify pointer to ClientListener in CustomClientInfo in destructor #205
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I would suggest to wait with merging this until #203 has been merged or it has been decided to delay it for now. |
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If #203 doesn't necessarily change the default behavior and we don't have concerns about regressions it is imo still on the list to possibly be merged. |
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Closing this since there have been enough changes to cause conflicts and it only mitigated an issue. |
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This mitigates (does not fix) a race condition when one thread calls
rmw_wait()and another callsrmw_destroy_client(). Whenrmw_wait()wakes up it callsCustomClientInfo->listener_, but both the instance ofCustomClientInfoand the object pointed to bylistener_have been destroyed. This nulls the fieldlistener_and hasrmw_wait()check this field before using it to reduce the likelyhood of a crash.I observed this race condition while debugging a CI test failure in ros2/rclcpp#488. The symptom seen is a SIGABRT on OSX when trying to lock
ClientListener.internalMutex_.I'm not sure what a real fix would look like.
rmw_wait()needs a way to tell the client it is holding onto has been destroyed. The other entities appear to be using the same pattern, so I suspect they suffer from similar race conditions too. (ticket to follow)