On Mon, Jun 14, 2010 at 11:20 PM, Don Stewart
v.dijk.bas:
Hello,
I've a short question about interruptible operations. In the following program is it possible for 'putMVar' to re-throw asynchronous exceptions even when asynchronous exception are blocked/masked?
newEmptyMVar >>= \mv -> block $ putMVar mv x
The documentation in Control.Exception about interruptible operations[1] confused me:
"Some operations are interruptible, which means that they can receive asynchronous exceptions even in the scope of a block. Any function which may itself block is defined as interruptible..."
I think the best definition of interruptible is in this paper:
www.haskell.org/~simonmar/papers/async.pdf
Section 5.3
Thanks for the link Don! Next time I will re-read the paper before asking ;-) The definition makes it clear indeed: "Any operation which may need to wait indefinitely for a resource (e.g., takeMVar) may receive asynchronous exceptions even within an enclosing block, BUT ONLY WHILE THE RESOURCE IS UNAVAILABLE" So I guess I can update my threads package to use MVars again. Nice! because they were a bit faster in an informal benchmark I performed some time ago. A later quote from 5.3 emphasizes the definition even more: "...an interruptible operation cannot be interrupted if the resource it is attempting to acquire is always available..." The following darcs patch makes the definition of interruptibility in the documentation in Control.Exception a bit clearer in this regard: http://bifunctor.homelinux.net/~bas/doc-interruptibility.dpatch Regards, Bas