SDK 2.0.0 OpenThread CoAP Client sample stack overflow

[wkpolara]

Using nRF Connect SDK v2.0.0 on Windows in VS Code.  Hardware is a U-Blox BMD340 demo kit with nRF52840.

We've built and run the following OpenThread sample applications successfully:

C:\ncs\v2.0.0\nrf\samples\openthread\cli

C:\ncs\v2.0.0\nrf\samples\openthread\coap_server

However, we're running into an issue with the OpenThread CoAP client sample project "out of the box"

C:\ncs\v2.0.0\nrf\samples\openthread\coap_client

The sample client project builds successfully, and starts up on the hardware, but when the kit button 2 is pressed to send a thread CoAp multicast message, it crashes with a stack overflow and reboots.  The UART command line outputs the following when the button is pressed:

uart:~$ ot state
leader
Done
[00:02:25.731,842] <inf> net_openthread: [N] RouterTable---: Allocate router id 21
[00:03:21.317,443] <inf> coap_client_utils: Send multicast mesh 'light' request
[00:03:21.317,596] <err> os: ***** MPU FAULT *****
[00:03:21.317,596] <err> os: Stacking error (context area might be not valid)
[00:03:21.317,626] <err> os: r0/a1: 0xaaaaaaaa r1/a2: 0xaaaaaaaa r2/a3: 0xaaaaaaaa
[00:03:21.317,657] <err> os: r3/a4: 0xaaaaaaaa r12/ip: 0xaaaaaaaa r14/lr: 0xaaaaaaaa
[00:03:21.317,657] <err> os: xpsr: 0xaaaaaa00
[00:03:21.317,687] <err> os: s[ 0]: 0x00000000 s[ 1]: 0x00000000 s[ 2]: 0x00000000 s[ 3]: 0x00000000
[00:03:21.317,687] <err> os: s[ 4]: 0x00000000 s[ 5]: 0x00000000 s[ 6]: 0x00000000 s[ 7]: 0x00000000
[00:03:21.317,718] <err> os: s[ 8]: 0x00000000 s[ 9]: 0x00000000 s[10]: 0x00000000 s[11]: 0x00000000
[00:03:21.317,718] <err> os: s[12]: 0x00000000 s[13]: 0x00000000 s[14]: 0x00000000 s[15]: 0xffffffff
[00:03:21.317,749] <err> os: fpscr: 0x00000000
[00:03:21.317,779] <err> os: Faulting instruction address (r15/pc): 0xaaaaaaaa
[00:03:21.317,810] <err> os: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
[00:03:21.317,840] <err> os: Current thread: 0x20003880 (sysworkq)
[00:03:21.497,100] <err> fatal_error: Resetting system
uart:~$ *** Booting Zephyr OS build v3.0.99-ncs1 ***

We're concerned this is happening to the sample "out of the box" with no modifications.  Is this a known issue with this sample in SDK v2.0.0?

[Amanda Hsieh]

Hi, 

There are many configs under https://github.com/nrfconnect/sdk-nrf/tree/main/samples/openthread/coap_client. Which config are you using?

Can you try to build with overlay-mtd.conf? It enables the Minimal Thread Device variant. See Configuration.

Regards,
Amanda

[wkpolara]

Hi Amanda,

I've using only the basic configuration, prj.conf.  I have not added any of the overlay configurations.  I'm following the "Testing" section of this page: https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/samples/openthread/coap_client/README.html

It is on step 3. Press Button 2 on the client node that the stack overflow occurs.

I tried building with overlay-mtd.conf, and in this configuration the stack overflow did not occur, and the CoAP light message is successfully sent to the server.

However, I'm interested in getting the basic FTD demo working.  Have you been able to reproduce the issue?

Thanks & Regards,

Walt

[wkpolara]

PS - I notice that in the overlay-mtd.conf, CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE = 2048.

By default in the basic configuration, it is only set to 1120.  Is the default value not enough for the FTD basic demo?

[Amanda Hsieh]

Yes, as you see in the log, the stack error is caused by the Stack overflow. Extending the system workqueue stack size could help fix the issue. 

-Amanda

[wkpolara]

I removed the mtd overlay. I then created a new overlay file that only contained CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE = 2048 and now the basic FTD CoAP client sample project is working and no longer crashing.

Is this an error in the default sample setup?