[Haskell-cafe] Cleaning up threads

Bas van Dijk v.dijk.bas at gmail.com
Wed Sep 15 01:55:48 EDT 2010

Also don't forget to unblock asynchronous exceptions inside
'someWorkToDo' otherwise you can't throw exceptions to the thread.
Note that 'finally' unblocks asynchronous exceptions but I consider
this a bug. In the upcoming base library this is fixed[1] but I would
advise to fix the code right now to not be surprised later.

Also note that the threads library correctly unblocks asynchronous
exceptions when necessary.



[1] http://hackage.haskell.org/trac/ghc/ticket/4035

On Wed, Sep 15, 2010 at 7:38 AM, Gregory Collins
<greg at gregorycollins.net> wrote:
> Bas van Dijk <v.dijk.bas at gmail.com> writes:
>> Don't forget to block asynchronous exception _before_ you fork in:
>>>        tid <- forkIO (someWorkToDo `finally` putMVar mv ())
>> Otherwise an asynchronous exception might be thrown to the thread
>> _before_ the 'putMVar mv ()' exception handler is installed leaving
>> your main thread in a dead-lock!
> Good catch, thank you,
> G
> --
> Gregory Collins <greg at gregorycollins.net>

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