Remove main stack customizations

[c1728p9]

Set all platforms to have a main stack twice as big as the default.

[c1728p9]

/morph test

[bridadan]

So much more room for activities! 😄

[mbed-bot]

Result: FAILURE

Your command has finished executing! Here's what you wrote!

/morph test

[0xc0170]

The targets should change the default stack size and not to edit sources, shouldn't they? Just to confirm that this change is to unify one place to edit the default main stack size?

[c1728p9]

The intention is to have the default stack the same across all platforms. That way code written for one device will not overflow if used on another.

[c1728p9]

/morph test-nightly

[mbed-bot]

Result: FAILURE

Your command has finished executing! Here's what you wrote!

/morph test-nightly

Output

mbed Build Number: 0

Test failed!

[bridadan]

Fixed the TLS failures! Awesome!

[c1728p9]

@pan- This doubles the size of the nrf51 stacks. Do you expect this to break any of the BLE examples?

[pan-]

I'm sorry but I don't get why the main stack should depends on DEFAULT_STACK_SIZE which itself depends on WORDS_STACK_SIZE which is not even configurable by target.

Looking at the configuration:

//   <o>Main Thread stack size [bytes] <64-32768:8><#/4>
#ifndef OS_MAINSTKSIZE
 #error "no target defined"
#endif

There is a define for the main stack size and every targets defines it.
What was the motivation behind this change ?
I would also add that OS_MAINSTKSIZE is still used to compute OS_STACK_SZ which at the end defines the size os_stack_mem. So, we're wasting space in this area by reserving space for the main stack twice.

@c1728p9 It won't break anything if it remains configurable like it was before (5.1.1).
This behavior was introduced with #2402 but I can't find any justification for this change. Static allocation is good but forcing a fixed size, non configurable, for the main stack isn't, especially when it is defined by every platform.

[0xc0170]

@c1728p9 It won't break anything if it remains configurable like it was before (5.1).
This behavior was introduced with #2402 but I can't find any justification for this change. Static allocation is good but forcing a fixed size, non configurable, for the main stack isn't, especially when it is defined by every platform.

@c1728p9 was there intention to make it non-configurable? This PR needs much more details ! Please amend the commit messages: at least to add - explaining why we are changing and what are the consequences. Because my question above was mainly about that one, same from @pan- .

[sg-]

@c1728p9 Going to close this. When RTX 5 lands we'll unify the stack size. This allows OOB to determine more run time failures if we shrink the main stack and document the new kernel and modifications and how to migrate. If you and @pan- can otherwise make an agreement please reopen.