Re: Avoid race condition with Popen.send_signal

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Date	Tue, 3 Jan 2012 19:58:57 +1100
Subject	Re: Avoid race condition with Popen.send_signal
From	Chris Angelico <rosuav@gmail.com>
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On Tue, Jan 3, 2012 at 7:44 PM, Jérôme <jerome@jolimont.fr> wrote:
> If so, I don't see how I can protect myself from that. Checking the process
> is alive and then hoping that the time interval for the race condition is so
> small that there are few chances for that to happen (because the OS
> quarantines PID numbers for a while, for instance) ?

The probability is extremely small. PIDs are generally allocated
sequentially, and obviously one won't be reallocated until the
previous process has terminated. You're looking at a narrow window of
opportunity between a check and an action; you don't really need to
worry about PID reuse within that window, unless there's a particular
reason to fear it (eg your process is very low priority, or there's a
lot of "process spinning" happening). Under normal circumstances, you
won't see a new process start up with the same PID for some time.

(I can't make a statement on Python's module, though.)

ChrisA

Thread

Re: Avoid race condition with Popen.send_signal Cameron Simpson <cs@zip.com.au> - 2012-01-03 12:44 +1100
  Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-02 19:16 -0800
    Re: Avoid race condition with Popen.send_signal Cameron Simpson <cs@zip.com.au> - 2012-01-03 15:53 +1100
      Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 06:52 -0800
    Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 09:44 +0100
      Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 06:12 -0800
        Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 16:09 +0100
          Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 09:58 -0800
            Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 19:45 +0100
    Re: Avoid race condition with Popen.send_signal Chris Angelico <rosuav@gmail.com> - 2012-01-03 19:58 +1100
      Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 06:20 -0800
    Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 10:38 +0100
      Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 07:03 -0800
        Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 17:24 +0100
        Re: Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 18:25 +0100

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