[GHC] #4154: Deadlock in Chan module

[GHC]

#4154: Deadlock in Chan module
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        Reporter:  NeilMitchell      |                Owner:  (none)
            Type:  bug               |               Status:  closed
        Priority:  high              |            Milestone:  8.4.1
       Component:  libraries/base    |              Version:  6.12.3
      Resolution:  fixed             |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Incorrect result  |  Unknown/Multiple
  at runtime                         |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Replying to [comment:9 mitar]:
 > What about my proposal:
 >
 > The only case where I have been using `isEmptyChan` was in my version of
 non-blocking `readChan`, returning Maybe. Is it possible to define instead
 of `isEmptyChan` some non-blocking version of `readChan` with
 `tryTakeMVar` and `tryPutMVar`?
 Out of curiosity, why not move to STM if you need these sorts of
 operations?

 I think the proposal is fine (assuming it's possible to implement safely;
 I am not familiar with the implementation of `Chan`). Do you want to put
 together a patch?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4154#comment:10>
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