[cryptonector]

This is called priority inversion.

One way to deal with this is to make it so that when a low-priority thread dequeues a message from a high-priority thread then the low-priority thread temporarily inherits the client's higher priority, then later goes back to its lower priority. The problem is identifying when to go back. Solaris doors was an IPC mechanism that did this well, but at the price of being synchronous -- when you throw asynchrony in that approach doesn't work, and you really do want asynchrony. If you trust the low-priority threads enough you can let them pick a priority according to that of the client they are servicing at any moment.