A simple semaphore class for bordeaux-threads inspired by SBCL's semaphore.
Obsolete! bordeaux-threads has its own built-in semaphores since version 0.8.6, so you should definitely use that instead of bt-semaphore.
bt-semaphore is available via Quicklisp. You can also clone the Git repo if you're curious:
cd ~/quicklisp/local-projects git clone https://github.com/rmoritz/bt-semaphore
There are seven functions of interest at the moment:
make-semaphorecreates a semaphore instance
wait-on-semaphoreblocks until the semaphore can be decremented (ie. its count > 0) or the timeout has expired
signal-semaphoreincrements the semaphore & wakes n waiting threads
try-semaphoredecrements the semaphore without blocking
semaphore-countreturns the current count of the semaphore
semaphore-waitersreturns the number of threads waiting on semaphore
semaphore-nameis an accessor for the semaphore's name slot
To illustrate, here's a tiny example:
(ql:quickload :bt-semaphore) (defun semaphore-demo () (defparameter sem (bt-sem:make-semaphore)) (defparameter lock (bt:make-lock)) (defparameter num 0) (format t "spawn 20 threads with 4s timeout~%") (loop repeat 20 do (bt:make-thread (lambda () (if (bt-sem:wait-on-semaphore sem :timeout 4) (bt:with-lock-held (lock) (incf num)))))) (format t "num is ~d~%" num) (sleep 0.33) (format t "there are ~d waiting threads~%~%" (bt-sem:semaphore-waiters sem)) (format t "signal 5 threads~%") (bt-sem:signal-semaphore sem 5) (sleep 0.33) (bt:with-lock-held (lock) (format t "num is ~d~%" num)) (format t "there are ~d waiting threads~%~%" (bt-sem:semaphore-waiters sem)) (format t "signal 10 threads~%") (bt-sem:signal-semaphore sem 10) (sleep 0.33) (bt:with-lock-held (lock) (format t "num is ~d~%" num)) (format t "there are ~d waiting threads~%~%" (bt-sem:semaphore-waiters sem)) (format t "4s sleep~%") (sleep 4) (bt:with-lock-held (lock) (format t "num is ~d~%" num)) (format t "there are ~d waiting threads~%~%" (bt-sem:semaphore-waiters sem)))
SEMAPHORE-DEMO at the REPL should produce the following output:
spawn 20 threads with 4s timeout num is 0 there are 20 waiting threads signal 5 threads num is 5 there are 15 waiting threads signal 10 threads num is 15 there are 5 waiting threads 4s sleep num is 15 there are 0 waiting threads
Working, but obsolete: bordeaux-threads has semaphore support since version 0.8.6. You should definitely be using that instead of bt-semaphore.
You can run the test suites to verify that everything is working as it should by invoking
(ql:quickload :bt-semaphore-test) or
Found one? Report it here, thanks.
- Ralph Moeritz (email@example.com)
Copyright (c) Ralph Moeritz 2013.
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