[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:  new
        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 slyfox):

 Some notes about the code
 which does '''threadWaitRead''' from haskell, but does not perform
 '''read()'''.

 For xmobar the bug was in polling on X11 socket from haskell
 code, and handling of sockets from C code (which ignored bad FD).

 Thus such code led to 100% CPU busy loop:
 {{{
     x11_ctx <- get_x11_ctx
     forever $ do
         threadWaitRead (x11_connection x11_ctx)
         x11_poll_events event_callback -- ignores -EBADF
 }}}

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4934#comment:18>
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