Comment 154 for bug 296167

> 1. what is the trigger for the deQueue to happen?

dequeuing events is part of the main loop.

> 2. what happens if an enqueue interrupts a dequeue?

nothing, in theory those two should be independent.

> The event order suggests that the dequeue never happens, or does not complete,
> or the next enqueue doesn't wait for an associated dequeue to complete. This
> type of problem looks like a missing semaphore or something like it.

Reports that the bug occurs more frequently under load indicate that too.
The one lead I have is that mi/mipointer.c stuff is being called both during
SIGIO handling and during event processing, but I haven't found any
significant overlap yet.