[GHC] #7993: ghc 7.6 (not 7.4) sometimes hangs at child process exit on s390x

[GHC]

#7993: ghc 7.6 (not 7.4) sometimes hangs at child process exit on s390x
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        Reporter:  cjwatson        |            Owner:
            Type:  bug             |           Status:  new
        Priority:  normal          |        Milestone:
       Component:  Runtime System  |          Version:  7.6.3
      Resolution:                  |         Keywords:
Operating System:  Linux           |     Architecture:  Other
 Type of failure:  Other           |       Difficulty:  Unknown
       Test Case:                  |       Blocked By:
        Blocking:                  |  Related Tickets:
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Comment (by nomeata):

 I tried to reproduce the problem by spawning lots of processes, but

 {{{
 import System.Process
 main = mapM_ (\_ -> readProcess "/bin/echo" ["hello", "world"] "")
 [0..10000]
 }}}

 did not deadlock.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7993#comment:2>
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