On Thu, Apr 8, 2010 at 9:15 PM, Isaac Dupree
I still would like to see examples of where it's needed, because I slightly suspect that wrapping possibly-blocking operations in an exception handler that does something appropriate, along with ordinary 'mask', might be sufficient... But I expect to be proved wrong; I just haven't figured out how to prove myself wrong.
Take my threads package, I uploaded to hackage yesterday, as an example. In Control.Concurrent.Thread.Group.fork I first increment numThreads before forking. When the fork thread terminates it should decrement numThreads and release the lock when it reaches zero so that potential waiters are woken up: http://hackage.haskell.org/packages/archive/threads/0.1/doc/html/src/Control... Now if an asynchronous exception is thrown during the takeMVar in decrement there's no way I can prevent not releasing the lock causing the waiters to deadlock. This could be solved by wrapping decrement in nonInterruptibleMask. regards, Bas