[GHC] #13194: Concurrent modifications of package.cache are not safe

[GHC]

#13194: Concurrent modifications of package.cache are not safe
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        Reporter:  arybczak          |                Owner:  arybczak
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  ghc-pkg           |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D3090
       Wiki Page:                    |
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Comment (by arybczak):

 While the patch is for 8.1, I adapted it for 8.0.2 (by basically adjusting
 MIN_VERSION_base to 4.9.1) and tested on Windows. It works fine, i.e.
 cabal using patched GHC was able to build dependencies for stack
 concurrently without failures (with -j8) a couple of times, whereas cabal
 using stock 8.0.1 failed every time with "permission denied" error during
 register phase of one of the packages.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13194#comment:8>
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