Quoting Ove Kaaven ovek@arcticnet.no:
Well, my theory is that in this situation, with the great new interactivity-boosting Linux scheduler, the wineserver is considered very interactive, and gets scheduled a lot more than the high-priority threads, just so it can satisfy the wait requests of the low-priority thread.
So what about introducing a new "scheduler flag" like the processor affinity flag. Some process may set itself to FLAG_NONITERACTIVE and the scheduler will never boost its priority. This can be allowed for non-root processes, too, as it doesn't increase the priority.