The submit queue channel was not actually increasing any performance. (peer).submit() would synchronously wait for all error results, and the call to (Wallet).SubmitMixMessage was already synchronized by the mixpool mutex.
Furthermore, this also fixes a deadlock that was observed after a mixing wallet with the RPC syncer mode reconnected to a restarted dcrd. Pair request messages were being submitted onto the channel with the client mutex held in (*Client).Dicemix. However, handleSubmitQueue had already exited and the client had not yet been restarted after dcrd reconnect, and was unable to be started due to the locked mutex.
The submit queue channel was not actually increasing any performance. (peer).submit() would synchronously wait for all error results, and the call to (Wallet).SubmitMixMessage was already synchronized by the mixpool mutex.
Furthermore, this also fixes a deadlock that was observed after a mixing wallet with the RPC syncer mode reconnected to a restarted dcrd. Pair request messages were being submitted onto the channel with the client mutex held in (*Client).Dicemix. However, handleSubmitQueue had already exited and the client had not yet been restarted after dcrd reconnect, and was unable to be started due to the locked mutex.