Understanding priority levels of ISR and FreeRTOS APIs

Kernel
16

A pictorial representation, if that helps:


            Logical      Numerical
           Priorities    Priorities
           +--------+    +-------+             ^
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             | Not masked by FreeRTOS kernel
           | Higher |    | Lower |             | ( FreeRTOS APIs can not be
           |        |    |       |             |    called from these ISRs. )
           |        |    |       |             |
           |        |    |       |             v
           +--------+    +-------+ <---------------- configMAX_SYSCALL_INTERRUPT_PRIORITY
           |        |    |       |             ^
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           | Lower  |    |Higher |             | Masked by FreeRTOS Kernel
           |        |    |       |             | ( FreeRTOS APIs can be
           |        |    |       |             |    called from these ISRs. ) 
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           |        |    |       |             |
           +--------+    +-------+             v

So in terms of NUMERICAL PRIORITIES, if configMAX_SYSCALL_INTERRUPT_PRIORITY == 4, then 4, 5, 6 and above are masked during critical sections.

Thanks.

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