#3160: No exception safety in Control.Concurrent.QSem QSemN and SampleVar
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Reporter: ChrisKuklewicz | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.6.1
Component: libraries/base | Version: 7.0.2
Resolution: | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: Incorrect result at runtime | Difficulty: Unknown
Testcase: | Blockedby:
Blocking: | Related:
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Comment(by ChrisKuklewicz):
I have updated SafeSemaphore to 0.9.0 on hackage and git,
http://github.com/ChrisKuklewicz/SafeSemaphore
I have done several different things with this release:
There is a new Control.Concurrent.SSem module based on STM that is dead
simple and replaces QSem and QSemN. I have not made a SampleVar
replacement with STM yet. The raw STM version is in
Control.Concurrent.STM.SSem. This does guarantee FIFO operation and so
has different starvation possibilities, especially with big and small
requests to waitN.
The MSem.hs file is now a literate MSem.lhs file. This has much more
elaborate comments discussing how the invariants are maintained. The
uninteruptableMask_ is only being used for the quick signal operation to
ensure bracket works properly.
The MSemN.hs file is now a literate MSemN.lhs file. This has extensively
documented invariants and short "proof" arguments that they are
maintained. The uninteruptableMask_ is used both in signal and to recover
from interrupted wait operators.
The new MSemN2.hs file is a variant of MSemN.lhs that does NOT use
uninteruptableMask_ in the wait operation at all. Instead it makes every
wait call check for the possible interruption of the previous wait. The
uninteruptableMask_ is not used on every signal call, but is used in the
with combinator to guard its call to signal.
For replacing QSem/QSemN/SampleVar I will update the patch with the
consensus design.
I have announced this 0.9.0 release to the Haskell-Cafe mailing list and
included a link to this ticket.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3160#comment:19>
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