[GHC] #4934: threadWaitRead works incorrectly on nonthreaded RTS

[GHC]

#4934: threadWaitRead works incorrectly on nonthreaded RTS
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        Reporter:  slyfox                       |            Owner:
            Type:  bug                          |           Status:  patch
        Priority:  normal                       |        Milestone:  ⊥
       Component:  Runtime System               |          Version:  7.0.1
      Resolution:                               |         Keywords:
Operating System:  Linux                        |     Architecture:  x86_64
 Type of failure:  Incorrect result at runtime  |  (amd64)
       Test Case:                               |       Difficulty:
        Blocking:                               |  Unknown
                                                |       Blocked By:
                                                |  Related Tickets:
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Comment (by Simon Marlow <marlowsd@…>):

 In [changeset:"9fd507e5758f4141ac2619f0db57136bcab035c6/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="9fd507e5758f4141ac2619f0db57136bcab035c6"
 Raise exceptions when blocked in bad FDs (fixes Trac #4934)

 Before the patch any call to 'select()' with 'bad_fd' led to:
 - unblocking of all threads
 - hiding exception for 'threadWaitRead bad_fd'

 The patch fixes both cases in this way:
 after 'select()' failure we iterate over each blocked descriptor
 and poll individually to see it's actual status, which is:
 - READY (move to run queue)
 - BLOCKED (leave in blocked queue)
 - INVALID (send an IOErrror exception)

 Signed-off-by: Sergei Trofimovich <slyfox at gentoo.org>
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4934#comment:26>
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