[GHC] #8209: Race condition in setNumCapabilities

[GHC]

#8209: Race condition in setNumCapabilities
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        Reporter:  akio              |            Owner:  simonmar
            Type:  bug               |           Status:  new
        Priority:  highest           |        Milestone:  7.8.1
       Component:  Runtime System    |          Version:  7.7
      Resolution:                    |         Keywords:
Operating System:  Unknown/Multiple  |     Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash     |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:
        Blocking:                    |  Related Tickets:
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Comment (by ezyang):

 Replying to [comment:7 akio]:
 > However, isn't there still a possibility that e.g. task 0 tries to
 acquire {{{cap->lock}}} in {{{waitForReturnCapability}}}, after {{{cap}}}
 is {{{stgFree}}}d in {{{setNumCapabilities}}}?

 Certainly that would be wrong, and a fix has to deal with it. (Note that
 while the memcpy problem I would expect to cause a deadlock, I would not
 expect this to cause a deadlock.)

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8209#comment:8>
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