Stack overflow

[Learner]

Hello,

I have been running this program without any problem then I added some code to read and write to flash using NVS when the error shown below appeared.

I am running a single ( main() ) thread application in Segger Embedded Studio v5.34a.

*** Booting Zephyr OS build v2.4.99-ncs1-rc1 ***
[00:00:13.434,600] [1;31m<err> os: ***** USAGE FAULT *****
[00:00:13.434,600] [1;31m<err> os: Stack overflow (context area not valid)
[00:00:13.434,600] [1;31m<err> os: r0/a1: 0x00000000 r1/a2: 0x0000cbfd r2/a3: 0x00000000
[00:00:13.434,600] [1;31m<err> os: r3/a4: 0x0000cbfd r12/ip: 0x207bc4ae r14/lr: 0x77fadffe
[00:00:13.434,600] [1;31m<err> os: xpsr: 0xfdd9ca00
[00:00:13.434,600] [1;31m<err> os: Faulting instruction address (r15/pc): 0x05221210
[00:00:13.434,631] [1;31m<err> os: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
[00:00:13.434,631] [1;31m<err> os: Current thread: 0x20000668 (unknown)
[00:00:13.696,472] [1;31m<err> fatal_error: Resetting system

If I the solution is to increase the stack size, how do I do it?

Can someone please help?

Kind regards

Mohamed

[Simon]

If the function that caused the stack overflow is called from main, increasing CONFIG_MAIN_STACK_SIZE would be the solution then.

Best regards,

Simon

[Learner]

Thank you Simon.

What is the solution if the function that is causing the stack overflow is not called from main() but few levels down the function call tree?

Kind regards

Mohamed

[Simon]

If the function is called further down the tree, but still within the main thread, you should still increase CONFIG_MAIN_STACK_SIZE. If you the function is called from within another thread, you should increas the stack size of that thread.

E.g. take a look at this DevZone case https://devzone.nordicsemi.com/f/nordic-q-a/70100/ecdsa-signing-crashes-when-implemented-with-bluetooth/288468#288468

where the hci_rx_thread was the cause and increasing CONFIG_BT_RX_STACK_SIZE solved the problem.

You may look into Ozone 3.22c as well, which makes it possible to do thread aware debugging. 

These may be useful as well: 

• https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.0/nrf/app_memory.html#memory-footprint-optimization 
• https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.5.0/zephyr/guides/flash_debug/thread-analyzer.html#thread-analyzer 
• https://devzone.nordicsemi.com/f/nordic-q-a/59838/why-there-is-no-main-in-zephyr-thread-sample-codes 

Best regards,

Simon

[Learner]

Hi Simon,

I increased the stack size to 8192 in prj.conf

CONFIG_MAIN_STACK_SIZE=8192

But I am still seeing this error upon entering main and before executing any of the application instructions.

In the SES debugger, the yellow arrow points to the first curly bracket  '{' in main(). I then click Go (F5) to move the cursor to the first instruction in main() then the error appears.

*** Booting Zephyr OS build v2.4.99-ncs1-rc1 ***
[00:00:41.795,043] <err> os: ***** USAGE FAULT *****
[00:00:41.795,043] <err> os: Stack overflow (context area not valid)
[00:00:41.795,043] <err> os: r0/a1: 0x245bc4ae r1/a2: 0x77fb5ffe r2/a3: 0x05821210
[00:00:41.795,074] <err> os: r3/a4: 0xbdd9cba6 r12/ip: 0x0405a049 r14/lr: 0x77faebb6
[00:00:41.795,074] <err> os: xpsr: 0x9ed6fa00
[00:00:41.795,074] <err> os: Faulting instruction address (r15/pc): 0x00aec010
[00:00:41.795,074] <err> os: >>> ZEPHYR FATAL ERROR 2: Stack overflow on CPU 0
[00:00:41.795,074] <err> os: Current thread: 0x20000668 (unknown)
[00:00:42.056,854] <err> fatal_error: Resetting system

It looks like something is going before main() starts running.

Please help.

Kind regards

Mohamed