[GHC] #13945: 'ghc-pkg update' fails due to bad file descriptor error

[GHC]

#13945: 'ghc-pkg update' fails due to bad file descriptor error
---------------------------------+----------------------------------------
        Reporter:  mpickering    |                Owner:  (none)
            Type:  bug           |               Status:  patch
        Priority:  high          |            Milestone:  8.2.2
       Component:  Compiler      |              Version:  8.2.1-rc3
      Resolution:                |             Keywords:
Operating System:  Linux         |         Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown  |            Test Case:
      Blocked By:                |             Blocking:
 Related Tickets:                |  Differential Rev(s):  Phab:D3897
       Wiki Page:                |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"f86de44dac0a6ca40c5fcd65f3a1944c45fa6011/ghc" f86de44/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="f86de44dac0a6ca40c5fcd65f3a1944c45fa6011"
 ghc-pkg: Try opening lockfiles in read-write mode first

 As pointed out in #13945, some filesystems only allow allow exclusive
 locks if the fd being locked was opened for write access. This causes
 ghc-pkg to fail as it first attempts to open and exclusively lock its
 lockfile in read-only mode to accomodate package databases for which we
 lack write permissions (e.g.  global package databases).

 Instead, we now try read-write mode first, falling back to read-only
 mode if this fails.

 Reviewers: austin

 Subscribers: rwbarton, thomie

 GHC Trac Issues: #13945

 Differential Revision: https://phabricator.haskell.org/D3897
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13945#comment:14>
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