On Wed, Aug 6, 2008 at 5:30 PM, Helmut Eller heller@common-lisp.net wrote:
- Nikodemus Siivola [2008-08-06 13:35+0200] writes:
and GET-LOCK has the wait wrapped in WITH-INTERRUPTS.
You meant GET-MUTEX, right?
Yes, (and it should be RELEASE-MUTEX in the code).
WITH-INTERRUPTS enabled interrupts only if there is an active ALLOW-WITH-INTERRUPTS lexically nested inside each WITHOUT-INTERRUPTS currently on stack. (This is what I was trying to explain while slightly too drunk to make a great deal of sense.)
Would the following also work?
(without-interrupts (allow-with-interrupts (with-mutex (lock) ...)
Assuming that WITH-MUTEX expands to the ordinary GET-MUTEX/RELEASE-MUTEX pair.
Yes.
WITH-MUTEX is essentially the code below, except that FROB-QUEUE bit is wrapped in WITH-LOCAL-INTERRUPTS (which is essentially ALLOW-WITH-INTERRUPTS+WITH-INTERRUPTS).
(let (got-it) (without-interrupts (unwind-protect (when (setf got-it (allow-with-interrupts (get-mutex lock))) ...frob-queue...) (when got-it (release-lock lock)))))
If this was performance sensitive code you'd want to write avoid the extra WITHOUT-INTERRUPTS, though.
Cheers,
-- Nikodemus