Arduino + FreeRTOS. SRAM Problem

[DrAngelOK]

Good day to all.
I am developing a project on Arduino Due + FreeRTOS.

After starting FreeRTOS, there are some problems with determining the available memory. Or FreeRTOS occupies the entire stack. Or the stack pointer somehow does not work correctly after its start. Help me.

Photo 1. Fully launched, without RTOS.
Photo 2. RTOS + 1 task launched.
Photo 3. Completely launched with RTOS.

[b707]

Please show the code you used for testing

[DrAngelOK]

/// <summary>
/// Определение свободной памяти контроллера
/// </summary>
void my_freeRam(void)
{
	char* ramstart = (char*)0x20070000; //адрес начала SRAM
	char* ramend = (char*)0x20088000; //адрес конца SRAM

	char* heapend = sbrk(0);
	register char* stack_ptr asm("sp");
	struct mallinfo mi = mallinfo();

	int ansi_dat_str = ANSI_INFO_ROW + 1;

	int RamAll;

	int RamStatic;
	int RamDynamic;
	int RamStack;

	int RamFreeSH;
	int RamFreeAll;

	RamAll = ramend - ramstart;
	
	RamStatic = &_end - ramstart;
	RamDynamic = mi.uordblks;
	RamStack = ramend - stack_ptr;

	RamFreeSH = stack_ptr - heapend;
	RamFreeAll = RamFreeSH + mi.fordblks;

	my_view_serial_print("RAM ALL:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamAll), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("Ram used (bytes): ", ansi_dat_str, ANSI_RAM_NAME_COL); ansi_dat_str += 1;
	my_view_serial_print("  static:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamStatic), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("  dynamic:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamDynamic), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("  stack:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamStack), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;

	my_view_serial_print("Ram Min:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamFreeSH), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("Ram Free:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (RamFreeAll), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	
	my_view_serial_print("arena:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.arena), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("ordblks:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.ordblks), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("hblks:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.hblks), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("hblkhd:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.hblkhd), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("fordblks:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.fordblks), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;
	my_view_serial_print("keepcost:", ansi_dat_str, ANSI_RAM_NAME_COL); my_view_serial_print((String) (mi.keepcost), ansi_dat_str, ANSI_RAM_VALUE_COL); ansi_dat_str += 1;

}

[westfw]

@DrAngelOK

I am developing a project on Arduino Due + FreeRTOS.
:

    RamStack = ramend - stack_ptr;

	RamFreeSH = stack_ptr - heapend;

Doesn't freeRTOS end up allocating a stack for each task, making the above calcs invalid for any particular task?

[DrAngelOK]

Here I am trying to understand.
It turns out there is no common stack?

If there is no FreeRTOS, the calculation is as follows:

FreeRTOS:

I think correctly?

[westfw]

@DrAngelOK

It turns out there is no common stack?

I'm not very familiar with FreeRTOS, but that's how most multi-taskers work.
Does this help: FreeRTOS Stack Overflow Checking
Also: Stack High Water Mark API
And: https://www.freertos.org/uxTaskGetSystemState.html

[DrAngelOK]

Thank you very much.
I have read all these links.

I thought that the common stack remains - where it should be.
And in a heap stacks of individual tasks.
Now I understand that after the launch of RTOS, there is probably no common stack.

[westfw]

@DrAngelOK

after the launch of RTOS, there is probably no common stack.

Probably ISRs and perhaps the FreeRTOS scheduler itself continue to use the original "common" stack.
(ISRs can "automatically" use a separate stack (sp_main) than "tasks" (sp_process), as part of the Cortex-M architecture. A non-RTOS application probably uses sp_main all of the time, instead of setting up a separate "process" stack; essentially similar to always running the chip in "privileged" mode.)

However, the whole idea that "the stack starts at the end of physical memory and grows downward until it collides with something" is pretty obsolete in the ARM world. Many build environments will set up a fixed-size stack at an arbitrary location, and can even put memory protection barriers around it to cause exceptions on overflow or underflow.