ruby - 如何跟踪 Ruby 中的死锁

Question

我使用 BrB为我用 Process#fork fork 的 Ruby 1.9 中的各种工作进程共享数据源:

Thread.abort_on_exception = true

fork do
  puts "Initializing data source process... (PID: #{Process.pid})"
  data = DataSource.new(files)

  BrB::Service.start_service(:object => data, :verbose => false, :host => host, :port => port)
  EM.reactor_thread.join
end

worker fork 如下:

8.times do |t|  
  fork do
    data = BrB::Tunnel.create(nil, "brb://#{host}:#{port}", :verbose => false)

    puts "Launching #{threads_num} worker threads... (PID: #{Process.pid})"    

    threads = []
    threads_num.times { |i|
      threads << Thread.new {
        while true
          begin
            worker = Worker.new(data, config)

          rescue OutOfTargetsError
            break

          rescue Exception => e
            puts "An unexpected exception was caught: #{e.class} => #{e}"
            sleep 5

          end
        end
      }
    }
    threads.each { |t| t.join }

    data.stop_service
    EM.stop
  end
end

这工作得非常完美，但在运行大约 10 分钟后，我收到以下错误:

bootstrap.rb:47:in `join': deadlock detected (fatal)
    from bootstrap.rb:47:in `block in <main>'
    from bootstrap.rb:39:in `fork'
    from bootstrap.rb:39:in `<main>'</pre>

这个错误并没有告诉我很多关于死锁实际发生的地方，它只是指向 EventMachine 线程上的 join。

如何追溯程序锁定的时间点？

Answer 1

它在父线程中锁定 join，该信息是准确的。要跟踪它在子线程中的锁定位置，请尝试将线程的工作包装在 timeout block 中。 .您需要暂时移除包罗万象的 rescue 以引发超时异常。

目前父线程尝试按顺序加入所有线程，阻塞直到每个线程完成。但是，每个线程只会在 OutOfTargetsError 时加入。可以通过使用短期线程并将 while 循环移动到父级来避免死锁。没有任何保证，但也许这样的事情会奏效？

8.times do |t|  
  fork do
    running = true
    Signal.trap("INT") do
      puts "Interrupt signal received, waiting for threads to finish..."
      running = false
    end

    data = BrB::Tunnel.create(nil, "brb://#{host}:#{port}", :verbose => false)

    puts "Launching max #{threads_num} worker threads... (PID: #{Process.pid})"    

    threads = []
    while running
      # Start new threads until we have threads_num running
      until threads.length >= threads_num do
        threads << Thread.new {
          begin
            worker = Worker.new(data, config)
          rescue OutOfTargetsError
          rescue Exception => e
            puts "An unexpected exception was caught: #{e.class} => #{e}"
            sleep 5
          end
        }
      end

      # Make sure the parent process doesn't spin too much
      sleep 1

      # Join finished threads
      finished_threads = threads.reject &:status
      threads -= finished_threads
      finished_threads.each &:join
    end

    data.stop_service
    EM.stop
  end
end