host: fix sendEvent/RemoveListener deadlock and send-on-closed panic - #8
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sendEvent held the listener read lock while blocking on unbuffered channel sends. A slow or disconnecting listener could block a send indefinitely, preventing RemoveListener from acquiring the write lock and causing a deadlock. It also left a window where RemoveListener could close a channel between sendEvent reading it from the map and sending to it, panicking on a send to a closed channel. Use non-blocking sends in sendEvent so the read lock is never held while blocked, and close the channel under the write lock in RemoveListener so no send can be in flight when it is closed.
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sendEvent held the listener read lock while blocking on unbuffered channel sends. A slow or disconnecting listener could block a send indefinitely, preventing RemoveListener from acquiring the write lock and causing a deadlock. It also left a window where RemoveListener could close a channel between sendEvent reading it from the map and sending to it, panicking on a send to a closed channel.
Use non-blocking sends in sendEvent so the read lock is never held while blocked, and close the channel under the write lock in RemoveListener so no send can be in flight when it is closed.