[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 simonmar):

 Getting a stack trace would probably help.  You want to make sure that GHC
 itself is built with `-debug`: set `GhcDebugged=YES` in your build.mk
 (this will slow down the build, but you can remove it later).  When the
 process hangs, attach to it with gdb and get a backtrace of all the
 threads.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7993#comment:4>
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