Hi,
I had a look at the code for Event (both versions) and Lock (but not the
others just yet) and it seemed fine. If you do lots of calls to
waitTimeout before a set you will accumulate old locks in the list, but
that won't cause any error that I can see, so it would only be a problem
in pathological cases.
I'm not sure there is a good way to test MVar algorithms. One way to do
it (which the Concurrent Haskell Debugger did online, IIRC:
http://www.informatik.uni-kiel.de/~fhu/chd/) is to reimplement IO to
explore different interleavings of the various MVar calls to look for
deadlocks. If you're testing STM, generally you can look to capture
invariants of your transactions and check that they hold after each
transaction (e.g. that if the state is Set, there shouldn't be any locks
waiting with an event).
Thanks,
Neil.
Roel van Dijk wrote:
Hello,
We wrote a small library (1) which offers a few extra synchronization
primitives. These primitives are found in the standard libraries of
languages like Java and Python, but not in Haskell.
Before releasing concurrent-extra on hackage, we would like some
comments on its name, design, implementation, documentation (2) and
general usefulness.
All primitives are implemented with MVars and IORefs, except for
Control.Concurrent.STM.Event.
There is a small test suite which tests some properties:
cabal configure -ftest
cabal build
cabal test
The test suite still needs to be expanded a great deal. We found that
testing concurrent algorithms is really hard. Now we test things like
"this shouldn't deadlock" by checking if it doesn't take too long. But
that doesn't feel very formal. Is there a more principled approach to
testing concurrent algorithms in Haskell?
After writing our version of a read-write lock we noticed the package
rwlock (3) on hackage. But there is a difference: rwlock is
implemented with STM while our version is implemented entirely with
MVars.
Regards,
Roel & Bas van Dijk
1 - http://code.haskell.org/~roelvandijk/code/concurrent-extra/
2 -
http://code.haskell.org/~roelvandijk/code/concurrent-extra/doc/html/concurrent-extra/index.html
3 - http://hackage.haskell.org/package/rwlock
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