[GHC] #12728: setnumcapabilities001 sometimes fails on Windows

[GHC]

#12728: setnumcapabilities001 sometimes fails on Windows
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        Reporter:  bgamari         |                Owner:  simonmar
            Type:  bug             |               Status:  new
        Priority:  high            |            Milestone:  8.0.2
       Component:  Runtime System  |              Version:  8.0.1
      Resolution:                  |             Keywords:
Operating System:  Windows         |         Architecture:  x86_64 (amd64)
 Type of failure:  Runtime crash   |            Test Case:
      Blocked By:                  |             Blocking:
 Related Tickets:                  |  Differential Rev(s):  Phab:D2617
       Wiki Page:                  |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"acc98510c5e32474b0bba9fba54e78df2b11078c/ghc" acc9851/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="acc98510c5e32474b0bba9fba54e78df2b11078c"
 Fix failure in setnumcapabilities001 (#12728)

 The value of enabled_capabilities can change across a call to
 requestSync(), and we were erroneously using an old value, causing
 things to go wrong later.  It manifested as an assertion failure, I'm
 not sure whether there are worse consequences or not, but we should
 get this fix into 8.0.2 anyway.

 The failure didn't happen for me because it only shows up on machines
 with fewer than 4 processors, due to the new logic to enable -qn
 automatically.  I've bumped the test parameter 8 to make it more
 likely to exercise that code.

 Test Plan: Ran setnumcapabilities001 many times

 Reviewers: niteria, austin, erikd, rwbarton, bgamari

 Reviewed By: bgamari

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D2617

 GHC Trac Issues: #12728
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12728#comment:5>
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