Avoid race condition with Popen.send_signal

Jérôme jerome at jolimont.fr
Mon Jan 2 18:09:14 EST 2012

Hi all.

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

process = Popen( args)

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)
if (None == process.returncode):

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 ?



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