[GHC] #8402: throwTo segfaults under -prof -threaded -with-rtsopts=N2

[GHC]

#8402: throwTo segfaults under -prof -threaded -with-rtsopts=N2
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        Reporter:  akio           |            Owner:
            Type:  bug            |           Status:  patch
        Priority:  normal         |        Milestone:
       Component:  Compiler       |          Version:  7.7
      Resolution:                 |         Keywords:
Operating System:  Linux          |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash  |       Difficulty:  Unknown
       Test Case:                 |       Blocked By:
        Blocking:                 |  Related Tickets:
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Changes (by akio):

 * status:  new => patch


Comment:

 The attached patch seems to fix this. I haven't figured out how I should
 validate it, since a normal validate run doesn't run many tests with
 profiling, so I just did {{{make}}} in
 {{{testsuite/tests/profiling/should_run}}}.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8402#comment:2>
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