A simple semaphore class for bordeaux-threads inspired by SBCL's semaphore.
bt-semaphore is available via Quicklisp. You
can also clone the Git repo if you prefer to use bleeding edge:
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
The basics are done. It's not yet a replacement for
we're getting there.
You can run the test suites to verify that everything is working as it
should by invoking
(ql:quickload :bt-semaphore-test) or
I'm not aware of any bugs, but if you believe you've found one, please do report it.
- Ralph Moeritz (firstname.lastname@example.org)
Copyright (c) Ralph Moeritz 2013.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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