Experimental Physics and
Industrial Control System

Simon Reiter via Tech-talk <tech-talk at aps.anl.gov> · Sat, 18 Jul 2020 08:59:32 +0200

I also thought about using ’spwan’ to create an independent process. But I was wondering why this is not mentioned at all on the pyepics page. And in fact, in that case it is also not clear to me what the advantage is of using CAProcess instead of Process.

I will try this now and report here again.

> On Jul 17, 2020, at 18:55, Michael Davidsaver <mdavidsaver at gmail.com> wrote:
> 
> On 7/17/20 9:33 AM, Michael Davidsaver wrote:
>> The python subprocess module shouldn't let this happen though since it does
>> fork() and then execv(), and the situation which I describe is only possible
>> if fork() is not followed by execv().
> 
> Oh wait.  CAProcess (which I've not seen previously) is using
> the multiprocessing module, which can do fork() without exec().
> In fact, this is the default on *NIX.  So this is likely or
> problem.  I think you'll need to use the 'spawn' or 'forkserver'
> method.
> 
> https://docs.python.org/3.7/library/multiprocessing.html#contexts-and-start-methods
> 
> https://github.com/pyepics/pyepics/blob/1f795c647458435cca0cf11b984b34fc11180c25/epics/multiproc.py

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System