Класс: LockFile Приватный

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# File 'lock_file.rb', line 18

def initialize(type, locked_path)
  @locked_path = locked_path
  lock_name = locked_path.basename.to_s
  @path = T.let(HOMEBREW_LOCKS/"#{lock_name}.#{type}.lock", Pathname)
  @lockfile = T.let(nil, T.nilable(File))
end

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# File 'lock_file.rb', line 26

def lock
  ignore_interrupts do
    next if @lockfile.present?

    path.dirname.mkpath

    begin
      lockfile = begin
        File.open(path, File::RDWR | File::CREAT)
      rescue Errno::EMFILE
        odie "The maximum number of open files on this system has been reached. " \
             "Use `ulimit -n` to increase this limit."
      end
      lockfile.fcntl(Fcntl::F_SETFD, Fcntl::FD_CLOEXEC)

      if lockfile.flock(File::LOCK_EX | File::LOCK_NB)
        # This prevents a race condition in case the file we locked doesn't exist on disk anymore, e.g.:
        #
        # 1. Process A creates and opens the file.
        # 2. Process A locks the file.
        # 3. Process B opens the file.
        # 4. Process A unlinks the file.
        # 5. Process A unlocks the file.
        # 6. Process B locks the file.
        # 7. Process C creates and opens the file.
        # 8. Process C locks the file.
        # 9. Process B and C hold locks to files with different inode numbers. 💥
        if !path.exist? || lockfile.stat.ino != path.stat.ino
          lockfile.close
          raise OpenFileChangedOnDisk
        end

        @lockfile = lockfile
        next
      end
    rescue OpenFileChangedOnDisk
      retry
    end

    lockfile.close
    raise OperationInProgressError, @locked_path
  end
end