[Haskell-cafe] Re: Asynchronous exception wormholes kill modularity

Bas van Dijk v.dijk.bas at gmail.com
Fri Apr 9 05:33:26 EDT 2010

On Fri, Apr 9, 2010 at 3:22 AM, Isaac Dupree
<ml at isaac.cedarswampstudios.org> wrote:
> OK, thanks for the link!  In fact, [tell me if my reasoning is wrong...], in
> that fork-definition, the 'putMVar' will never block, because there is only
> putMVar one for each created MVar.

Yes that's correct.

> I seem to remember that any execution of
> putMVar that does not *actually* block is guaranteed not be interrupted by
> asynchronous exceptions (if within a Control.Exception.block) -- which would
> be sufficient.  Is my memory right or wrong?

The following documentation seems to suggest that "any function which
_may_ itself block is defined as interruptible":


That doesn't answer your question precisely however.

If it is the case that operations are only interruptible when they
actually block then I don't need a nonInterruptibleMask in this last
example. However I still need one in my first example because the
takeMVar in decrement may absolutely block.



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