[GHC] #16147: ghc-pkg deadlocks on macOS

[GHC]

#16147: ghc-pkg deadlocks on macOS
-------------------------------------+-------------------------------------
           Reporter:  rvl            |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Runtime        |           Version:  8.6.3
  System                             |
           Keywords:                 |  Operating System:  MacOS X
       Architecture:  x86_64         |   Type of failure:  Incorrect result
  (amd64)                            |  at runtime
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 If I run this script on macOS, after about 15 minutes, a `ghc-pkg` process
 will deadlock.

 {{{#!sh
 #!/usr/bin/env bash

 out=`pwd`/testing-package-db

 rm -rf $out

 cabal update
 cabal install random

 mkdir -p $out
 ghc-pkg init $out/package.conf.d

 while true; do
     ghc-pkg --package-db $HOME/.ghc/x86_64-darwin-8.6.3/package.conf.d
 dump | ghc-pkg --force --package-db $out/package.conf.d register -
 done
 }}}

 Output from `sw_vers`:
 {{{
 ProductName:    Mac OS X
 ProductVersion: 10.12.6
 BuildVersion:   16G29
 }}}

 This GHC build comes from the latest nixpkgs-18.09. I have also attached a
 nix file to build test scripts.

 We noticed that if we edited the ghc-pkg binary to link with the threaded
 RTS, then we could not reproduce the deadlock (after running the test
 script for 24 hours).

 Attached is the output from `/usr/bin/sample` for the stuck process, and
 the `otool -L ghc-pkg` output.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16147>
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