Final bikeshedding call: Fixing Control.Exception.bracket

[Simon Marlow]

On 19/11/2014 23:07, Ganesh Sittampalam wrote:
> On 13/11/2014 10:44, Simon Marlow wrote:
>> On 13/11/2014 07:47, Merijn Verstraaten wrote:
>
>>> A new version would look like:
>>>
>>> bracket before after thing =
>>>     mask $ \restore -> do
>>>       let atomicAfter = uninterruptibleMask . after
>>>       a <- before
>>>       r <- restore (thing a) `onException` atomicAfter a
>>>       _ <- atomicAfter a
>>>       return r
>>>
>>> Slightly different versions are possible and the other relevant
>>> bracketing functions mentioned in this thread can be treated similarly.
>>
>> Since we would need this for catch too, the sensible thing to do (if we
>> decide to go ahead with this) would be to change the implementation of
>> catch in the RTS from masking the exception handler to
>> uninterruptibleMask.  That would mean that at least for catch there
>> would be no additional overhead, and it would make the modifications to
>> the other operations simpler in some cases.
>
> If this isn't done in the RTS, is there a possibility of an async
> exception slipping in between the exception handler starting and the
> uninterruptibleMask starting?

No, because the exception handler is masked.

Cheers,
Simon