FreeRTOS SMP: Idle tasks affinity

Kernel
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Hi, I am currently using FreeRTOS 11.1.0 in Symmetric MultiProcessing and I am encountering a strange error while executing a simple example program. I have defined the traceTASK_SWITCHED_IN and traceTASK_SWITCHED_OUT to track the tasks execution on 2 cores and this is the result:

---------- New Session ----------
Hello from Freertos example main
[TASK] IDLE0 SWITCHED-IN ## CORE 0
[TASK] IDLE1 SWITCHED-OUT ## CORE 1
[TASK] Tmr Svc SWITCHED-IN ## CORE 1
[TASK] IDLE0 SWITCHED-OUT ## CORE 0
[TASK] IDLE1 SWITCHED-IN ## CORE 0
[TASK] IDLE1 SWITCHED-OUT ## CORE 0
HALT: Task IDLE1 overflowed its stack.

Aside from increasing the stack size of the idle tasks (which btw didn’t solve the problem), I also investigated why CORE0 executes IDLE1 since, from my understanding, each core can only execute its idle task. I found out that the core affinity of idle tasks is set to -1 so they can be scheduled on every available core. Is this the correct behavior?

2

This is indeed because the IDLE tasks are not created with a fixed affinity in the SMP kernel. See here. So the behavior that you see is correct.

1 Like
3

Have you found the reason for stack overflow?

4

Nope, not yet. I am currently trying to reliably trace both cores during the program execution.

5

On smp，if set configSUPPORT_STATIC_ALLOCATION , you can refer FreeRTOS/FreeRTOS/Test/CMock/smp/multiple_priorities_no_timeslice/multiple_priorities_no_timeslice_utest.c at 91659446648a00f24b0b8af6327230658cc65c07 · FreeRTOS/FreeRTOS · GitHub to setup passive idle task sack. Hope this help you.

6

Thank you. Are you suggesting to use static allocation to check if the program behaves differently with dynamic and static allocation? At the moment I have configSUPPORT_STATIC_ALLOCATION disabled.