[GHC] #9321: Support for waiting on multiple MVars

[GHC]

#9321: Support for waiting on multiple MVars
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              Reporter:  schyler     |             Owner:  simonmar
                  Type:  feature     |            Status:  new
  request                            |         Milestone:
              Priority:  normal      |           Version:  7.8.3
             Component:  Runtime     |          Keywords:  mvar
  System                             |  Operating System:  Unknown/Multiple
            Resolution:              |   Type of failure:  None/Unknown
Differential Revisions:              |         Test Case:
          Architecture:              |          Blocking:
  Unknown/Multiple                   |
            Difficulty:  Unknown     |
            Blocked By:              |
       Related Tickets:              |
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Comment (by carter):

 likewise, it seems like the async package  provides a version of this
 https://hackage.haskell.org/package/async-2.0.1.5/docs/Control-Concurrent-
 Async.html#g:6

 waitEither :: Async a -> Async b -> IO (Either a b)

 among others.

 do you have a specific test case where the mvar or async approaches are
 too slow?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9321#comment:4>
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