[GHC] #3875: DPH QuickHull example crashes on SPARC with -N > 1

[GHC]

#3875: DPH QuickHull example crashes on SPARC with -N > 1
-------------------------------+--------------------------------------------
    Reporter:  benl            |        Owner:  benl         
        Type:  bug             |       Status:  assigned     
    Priority:  high            |    Milestone:  6.12.2       
   Component:  Runtime System  |      Version:  6.13         
    Keywords:                  |   Difficulty:               
          Os:  Solaris         |     Testcase:               
Architecture:  sparc           |      Failure:  Runtime crash
-------------------------------+--------------------------------------------

Comment(by benl):

 This looks like a race in the bale-out code at the bottom of
 `eval_thunk_selector`. An instrumented version of the code shows these
 events. The program was previously crashing when it tried to dereference
 the last, misaligned pointer.

 {{{
 tid= 3 p=fece84f4 entering eval_thunk_selector.
 tid= 3 p=fece84f4 info_ptr_table=19a0750
 tid= 3 p=fece84f4 bailing out
 tid= 0 p=fece84f4 entering eval_thunk_selector.
 tid= 0 p=fece84f4 info_ptr_table=fec96b21 BLERGH!!!!!! stopping program
 }}}

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Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/3875#comment:7>
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