[GHC] #8591: Concurrent executions of ghc-pkg can cause inconstant package.cache files

[GHC]

#8591: Concurrent executions of ghc-pkg can cause inconstant package.cache files
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              Reporter:  janm        |            Owner:  pgj
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:
             Component:  Package     |          Version:  7.6.3
  system                             |         Keywords:  ghc-pkg race
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:  FreeBSD     |       Difficulty:  Unknown
       Type of failure:  Other       |       Blocked By:
             Test Case:              |  Related Tickets:
              Blocking:              |
Differential Revisions:              |
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Comment (by janm):

 Thanks for the reply. A quick code inspection of the renameFile function
 shows the same race. The function is atomic for single threaded execution
 (ie. all or nothing for the updated file), but updates can be lost when
 there is concurrent execution of two processes.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8591#comment:7>
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