PWM.set_duty_cycle segmentation fault - but only using python3.6

[MrBillium]

New clean install using official stretch 2017-10-10 IoT image which includes Python 3.53. Calling set_duty_cycle throws Segment fault if run using Python3.60 or 3.63 venvs but no error using included Python3 or python 3.53 venv
I have narrowed it down to the following simple code. Any ideas?

Bill

Code file pwmtest.py

`import Adafruit_BBIO.PWM as PWM

pin = 'P8_13'
PWM.start(pin, 50, 2000, 1)
PWM.set_duty_cycle(pin, 30)`

results for venv's
venvs/py360/bin/python /tmp/pwmtest.py - Segment fault
venvs/py363/bin/python /tmp/pwmtest.py - Segment fault
venvs/py353/bin/python /tmp/pwmtest.py - No error

[pdp7]

@MrBillium thanks for opening this issue. I'll attempt to reproduce and investigate the cause.

[pdp7]

@MrBillium which kernel is running when you get the seg fault?

[pdp7]

@MrBillium who did you install Python 3.6? I don't see it the repo. Just Python 3.5.

[MrBillium]

Python 3.6 was built from source and works fine otherwise - I built as follows
./configure --enable-optimizations
make
make altinstall

Using kernal 4.49

root@beaglebone:# /opt/scripts/tools/version.sh
git:/opt/scripts/:[d36fe9a7be9ebfc872b10a470e904ab4c61c4516]
eeprom:[A335BNLTBBG115081628]
dogtag:[BeagleBoard.org Debian Image 2017-10-10]
bootloader:[eMMC-(default)]:[/dev/mmcblk1]:[U-Boot 2017.09-00002-g0f3f1c7907]
kernel:[4.4.91-ti-r133]
nodejs:[v6.11.4]
uboot_overlay_options:[enable_uboot_overlays=1]
uboot_overlay_options:[disable_uboot_overlay_video=1]
uboot_overlay_options:[disable_uboot_overlay_audio=1]
uboot_overlay_options:[disable_uboot_overlay_adc=1]
uboot_overlay_options:[uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-4-TI-00A0.dtbo]
uboot_overlay_options:[enable_uboot_cape_universal=1]
pkg:[bb-cape-overlays]:[4.4.20171009.0-0rcnee1stretch+20171009]
pkg:[bb-wl18xx-firmware]:[1.20170829-0rcnee1stretch+20170829]
pkg:[firmware-ti-connectivity]:[20170823-1rcnee0stretch+20170830]
root@beaglebone:~#

[pdp7]

@MrBillium Is this the release that I should compile?
https://www.python.org/downloads/release/python-363/

[MrBillium]

Yes 3.63 is the latest – I had the same problem with 3.60. Bill From: Drew Fustini [mailto:notifications@github.com] Sent: Sunday, November 19, 2017 5:40 PM To: adafruit/adafruit-beaglebone-io-python <adafruit-beaglebone-io-python@noreply.github.com> Cc: MrBillium <bilmar19@gmail.com>; Mention <mention@noreply.github.com> Subject: Re: [adafruit/adafruit-beaglebone-io-python] PWM.set_duty_cycle segmentation fault - but only using python3.6 (#189) @MrBillium <https://github.com/mrbillium> Is this the release that I should compile? https://www.python.org/downloads/release/python-363/ — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#189 (comment)> , or mute the thread <https://github.com/notifications/unsubscribe-auth/ANnql5ASWbGuY1F6xXe1146gd7cpVZ0bks5s4K5LgaJpZM4QaJxp> . <https://github.com/notifications/beacon/ANnql_2hxyzXiRlBlOh7lnm0WxK-cTmIks5s4K5LgaJpZM4QaJxp.gif>

[MrBillium]

Note that if you compile Python on a BB it will take 6-7 hours! Bill From: Drew Fustini [mailto:notifications@github.com] Sent: Sunday, November 19, 2017 5:40 PM To: adafruit/adafruit-beaglebone-io-python <adafruit-beaglebone-io-python@noreply.github.com> Cc: MrBillium <bilmar19@gmail.com>; Mention <mention@noreply.github.com> Subject: Re: [adafruit/adafruit-beaglebone-io-python] PWM.set_duty_cycle segmentation fault - but only using python3.6 (#189) @MrBillium <https://github.com/mrbillium> Is this the release that I should compile? https://www.python.org/downloads/release/python-363/ — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#189 (comment)> , or mute the thread <https://github.com/notifications/unsubscribe-auth/ANnql5ASWbGuY1F6xXe1146gd7cpVZ0bks5s4K5LgaJpZM4QaJxp> . <https://github.com/notifications/beacon/ANnql_2hxyzXiRlBlOh7lnm0WxK-cTmIks5s4K5LgaJpZM4QaJxp.gif>

[pdp7]

@RobertCNelson would you be able to package Python 3.6.3 for BeagleBone?

[RobertCNelson]

@pdp7 so Python 3.6.3 is in Buster:
https://packages.debian.org/buster/python3
Grab this image for testing:

https://rcn-ee.net/rootfs/bb.org/testing/2017-11-19/buster-iot/

Regards,

[pdp7]

@RobertCNelson thanks

@MrBillium I'm running this Debian Buster image linked above with 4.14.0-ti-r9 kernel. I get a seg fault when trying to run PWM.set_duty_cycle() on Python 2.7.14 and Python 3.6.3.

I'll investigate further to see why that occurs.

fyi - here are the full results:

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python ~/issue189.py
Segmentation fault
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 ~/issue189.py
Segmentation fault
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python --version     
Python 2.7.14
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 --version
Python 3.6.3
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python ~/issue189-no-set_duty_cycle.py
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 ~/issue189-no-set_duty_cycle.py

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ cat ~/issue189-no-set_duty_cycle.py
import Adafruit_BBIO.PWM as PWM

pin = 'P8_13'
PWM.start(pin, 50, 2000, 1)
#PWM.set_duty_cycle(pin, 30)

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ cat ~/issue189.py                  
import Adafruit_BBIO.PWM as PWM

pin = 'P8_13'
PWM.start(pin, 50, 2000, 1)
PWM.set_duty_cycle(pin, 30)

I've added some logging and it seems the problem occurs in PyArg_ParseTupleAndKeywords():

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python ~/issue189.py 
pwm_start: call pwm_set_duty_cycle()
pwm_set_duty_cycle(): enter
pwm_set_duty_cycle(): call lookup_exported_pwm()
pwm_set_duty_cycle(): pwm=0x2706d10
pwm_set_duty_cycle(): buffer=250000
pwm_set_duty_cycle(): call lseek()
pwm_set_duty_cycle(): call write()
pwm_set_duty_cycle(): return BBIO_OK
py_set_duty_cycle(): enter
py_set_duty_cycle(): call PyArg_ParseTupleAndKeywords()
Segmentation fault

for reference, versions of python on Debian 9.2 (2017-10-17 image) where there is no error:

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python --version
Python 2.7.13
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 --version
Python 3.5.3
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python ~/issue189.py 

[pdp7]

I have compiled Python 3.6.3 from source and installed in Debian 9.2 (2017-10-17 image). PWM.set_duty_cycle() does cause a segmentation fault with Python 3.6.3.

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ cat /etc/dogtag 
BeagleBoard.org Debian Image 2017-10-17
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ cat /etc/debian_version 
9.2
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python --version
Python 2.7.13
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 --version
Python 3.5.3
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3.6 --version
Python 3.6.3
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python2 ~/issue189.py 
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3 ~/issue189.py 
debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ python3.6 ~/issue189.py 
Segmentation fault

[pdp7]

I'm investigating if a change in Python 3.6 versus 3.5 triggered this seg fault issue for the call to PyArg_ParseTupleAndKeywords() in py_set_duty_cycle().

This could be relevant:
What’s New In Python 3.6: Build and C API Changes

PyArg_ParseTupleAndKeywords() now supports positional-only parameters. Positional-only parameters are defined by empty names. (Contributed by Serhiy Storchaka in bpo-26282).

[pdp7]

I've not been able to determine thus far what is causing the issue for Python 3.6. Here are the functions that call PyArg_ParseTupleAndKeywords(). I'm going to investigate them further:

source/py_gpio.c

// python function setup(channel, direction, pull_up_down=PUD_OFF, initial=None, delay=0)
static PyObject *py_setup_channel(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "si|iii", kwlist, &channel, &direction, &pud, &initial, &delay))

// python function add_event_callback(gpio, callback, bouncetime=0)
static PyObject *py_add_event_callback(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "sO|i", kwlist, &channel, &cb_func, &bouncetime))

// python function add_event_detect(gpio, edge, callback=None, bouncetime=0
static PyObject *py_add_event_detect(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
   if (!PyArg_ParseTupleAndKeywords(args, kwargs, "si|Oi", kwlist, &channel, &edge, &cb_func, &bouncetime))

source/py_pwm.c

// python function start(channel, duty_cycle, freq)
static PyObject *py_start_channel(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s|ffi", kwlist, &channel, &duty_cycle, &frequency, &polarity)) {

// python method PWM.set_duty_cycle(channel, duty_cycle)
static PyObject *py_set_duty_cycle(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s|f", kwlist, &channel, &duty_cycle))

// python method PWM.set_frequency(channel, frequency)
static PyObject *py_set_frequency(__attribute__ ((unused)) PyObject *self, PyObject *args, PyObject *kwargs)
    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s|f", kwlist, &channel, &frequency))

[pdp7]

PWM.set_frequency() also causes a seg fault with Python 3.6:

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ cat ~/pwm-test.py
import Adafruit_BBIO.PWM as PWM 
PWM.start("P9_14", 50)
PWM.set_frequency("P9_14", 10)

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python$ sudo python3.6 ~/pwm-test.py
Segmentation fault