RE: self piping and context switching

["David Schwartz" <davids@webmaster.com>]

> Assume a thread is monitoring a set of fd's which include both ends of
> a pipe (using poll, for example). If the thread writes to the pipe (in
> order to notify itself for whatever reason) is it reasonable to expect
> that it will be able to return to its poll loop and get the event
> without a context switch? (provided it quickly returns to the poll
> loop).

	It's reasonable to expect that this will be the most common case and the
one to optimize. It is unreasonable to fail if this doesn't happen, since
it's not guaranteed to happen. Note that if by "without a context switch"
you really mean without another thread getting a chance to run, then it is
totally unreasonable. On SMP systems and with hyper-threading, threads can
run concurrently.

	DS