The signalfd implementation will use this.

We'll replace the process field next, but the accessor function will
remain.

We'll need direct access to the Arc in some of the folllowing patches.

Closing a socket while its read half still has data causes the
connection to be reset. This changes the error returned on the other
side of the connection when there's no more data.

…rupt

Code in timer interrupts may not allocate and may only take locks that
disable timer interrupts.

It turns out that there is a file descriptor type, signalfd, whose
readiness depends on which thread is polling it.

The main table might not have routes, but the local table usually does.

This is an alternative for operations that might seem like they're
ready, but don't actually return yet e.g. receive operations with
WAITALL.

The ell tests add coverage for signalfd, epoll, and netlink.

This only worked if StartNextAp was called by all APs in order. It's a
miracle this didn't break earlier.

I'm guessing this can happen because the align_up make it too big.