If we had already processed a couple of queued events by the time we were
told to un-nest the event loop, we'd put the entire current batch at the
head of the outer queue. This meant that we might end up trying to process
the same events multiple times.
Let's not do that. :^)
Add a trivial CSafeSyscall template that calls a callback until it stops
returning EINTR, and use it everywhere we use select() now.
Thanks to Andreas for the suggestion of using a template parameter for
the syscall function to invoke.
This way, CNotifier can mutate state to its little heart's content
without destroying the world when the global CNotifier hash changes
during delivery.
This patch generalizes the concept used in Piano to wake up the event loop
so it can react to something happening on a secondary thread.
Basically, there's a pipe who is always part of the file descriptor set we
pass to select(), and calling wake() simply writes a little to that pipe.
Don't process any more events. We already prepend the remaining events in
this loop to the outer loop if needed.
If there were any more events queued after the exit request, the iteration
code would make an invalid access into 'queued_events'.
Fixes#300.
