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Avoid race condition with Popen.send_signal

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Hi all.

When a subprocess is running, it can be sent a signal with the send_signal
method :

process = Popen( args)
process.send_signal(signal.SIGINT)

If the SIGINT is sent while the process has already finished, an error is
raised : 

  File "/usr/lib/python2.7/subprocess.py", line 1457, in send_signal
    os.kill(self.pid, sig)
OSError: [Errno 3] Aucun processus de ce type

To avoid this, I can check that the process is still alive :

process = Popen( args)
process.poll()
if (None == process.returncode):
    process.send_signal(signal.SIGINT)

It makes safer, but there is still an issue if the process ends between
poll() and send_signal().

What is the clean way to avoid this race condition ?

Should I use try/except to catch the error or is there a more elegant way to
go ?

Thanks.

-- 
Jérôme

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Thread

Avoid race condition with Popen.send_signal Jérôme <jerome@jolimont.fr> - 2012-01-03 00:09 +0100
  Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-02 17:19 -0800
    Re: Avoid race condition with Popen.send_signal Heiko Wundram <modelnine@modelnine.org> - 2012-01-03 13:31 +0100
      Re: Avoid race condition with Popen.send_signal Adam Skutt <askutt@gmail.com> - 2012-01-03 05:40 -0800
        Re: Avoid race condition with Popen.send_signal Heiko Wundram <modelnine@modelnine.org> - 2012-01-03 14:56 +0100

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