On Sep 11, 2014, at 2:29 PM, Ervin Hegedüs <airw...@gmail.com> wrote:
> Hi Travis,
>
> On Thu, Sep 11, 2014 at 02:06:48PM -0700, Travis Griggs wrote:
>>
>> On Sep 11, 2014, at 11:18 AM, Chris “Kwpolska” Warrick <kwpol...@gmail.com>
>> wrote:
>>
>>> Depends what you want.
>>
>> Mine is not a web service. My main.py looks like this:
>>
>> #!/usr/bin/env python3
>>
>> import cycle
>> import pushTelemetry
>> from threading import Thread
>>
>> def main():
>> Thread(target=pushTelemetry.udpLoop).start()
>> Thread(target=cycle.cycleLoop).start()
>>
>> if __name__ == '__main__':
>> main()
>>
>> It basically creates two threads, one which does some local processing and
>> control, the other which periodically does reporting via udp packets. I use
>> the dual threads because they both work with a shared serial port at times,
>> so I have to synchronize access through that.
>>
>> What I want is to have this startup, after my board has it’s networking
>> layer up and running (and hopefully a valid ip address by then), and to just
>> keep running forever
>
> may be you think about the fork(), eg:
>
> if __name__ == "__main__":
> ...other codes, eg. drop root privileges, ...
> ...check arguments...
> try:
> pid = os.fork()
> if pid > 0:
> #print "Daemon started (pid: %d)" % (pid)
> sys.exit(0)
> except OSError, e:
> print >>sys.stderr, "fork #1 failed: %d (%s)" % (e.errno, e.strerror)
> sys.exit(1)
>
> os.chdir("/")
> os.setsid()
> os.umask(0)
>
> # do second fork
> try:
> pid = os.fork()
> if pid > 0:
> #print "Daemon started (pid: %d)" % (pid)
> sys.exit(0)
> except OSError, e:
> print >>sys.stderr, "fork #2 failed: %d (%s)" % (e.errno, e.strerror)
> sys.exit(1)
>
> main()
OK, I’m probably going to show my naivety about something simple here…
I thought a “fork” essentially created a memory copy of the original process
and let it go off running. The problem is, in the bowels of the code executing
in those loops, I access a single instance of a threading.RLock, so that I can
avoid both threads trying to do transactions with a single serial port at the
same time. If I end up with two copies of the base process, unhooked from their
parent, does that RLock still remain valid between the two? I thought since
they were complete different copies of the same memory, they would no longer be
coordinated.
Is this a day where I discover something new?
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