1.4.4 stack on startup is sometimes larger

[AlexKlimaj]

I recently updated to 1.4.4. I noticed that I started getting a random hardfault on boot and traced it to the AFBR driver sometimes using more stack causing it to overrun the amount allocated to the task.

Currently I have 1872 bytes allocated to the task. After increasing that, I found that the AFBR sometimes uses 2068 on startup instead of 1876.

Upon power cycling, it appears to be random how much stack it uses. Can you tell me why this is the case?

[c-berger]

Hi Alex,

I am not aware of such a issue. The startup sequence should be deterministic. But since there is real hardware involved, it could happen that the path through the code is slightly different depending on what values are obtained from the device. For example, the PLL lock time may vary slightly each time resulting in more or less repetitions when polling its state via SPI.

Just to make sure, when you talk about startup, you mean the Argus_Init function? Further, when you say random, everything stays the same, i.e. same configuration, same device, etc.?
Does this happen for a specific device only (which one?) or can you reproduce it with multiple devices (also, which ones?)?
How did you measure the stack? Simply by checking what memory has been changed after calling Argus_Init? Just wondering if it could have the same stack usage but sometimes not using the allocated space...

Best regards,
Christoph

[AlexKlimaj]

On the same device through different power cycles, the stack will vary on startup. The behavior is the same across multiple units.

I only noticed this after upgrading to 1.4.4. It might be occurring on 1.3.5 but didn't cause a hardfault because it used less overall stack.

Stack is measured in nuttx with top.

[c-berger]

Ok, thanks for the information.
Is it possible to simply increase the stack size to get rid of the issue?

[AlexKlimaj]

Yes I increased the stack and the hardfault was resolved. But I would like to know what the library is doing internally that it can dynamically change the amount of stack required.