#5238: throwSTM+catchSTM pollutes the masking state
-----------------------------------+----------------------------------------
Reporter: mikhail.vorozhtsov | Owner: simonmar
Type: bug | Status: new
Priority: high | Milestone: 7.2.1
Component: Runtime System | Version: 7.1
Keywords: stm | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by mikhail.vorozhtsov):
Replying to [comment:2 simonmar]:
> Is it sensible for `catchSTM` to catch asynchronous exceptions, and to
be able to mask inside STM?
Yes. I intend to use it like this:
{{{
mask $ \restore → do
ioBefore
atomically $ restore $ aRatherLongTransactionWithRetries
ioAfter
}}}
where `mask` has type
{{{
MonadException µ η ⇒ ((∀ μ' η' β . MonadException μ' η' ⇒ μ' β → μ' β) → μ
α) → μ α
}}}
(which basically means that it can restore the masking state in both IO
and STM, as well as in any stack of transformers which has one of them as
the base, via the monad-control package machinery).
This way it would be guaranteed that if the computation is interrupted
then the transaction is not committed.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5238#comment:3>
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