This might be a bit obscure and I might be jumping at shadows here.
I am running FreeRTOS 7.4.0 on an EFM32LGxxx (Cortex-M3 core). The OS ticks are implemented using the on-chip RTC and the system has my own tickless sleep mode implementation.
I have an ISR which is active during the tickless sleep, and this has a call to xTimerStartFromISR(). I am passing a valid memory address in for the second parameter - this seems to be essential to make sure that xQueueSendToBackFromISR() is called instead of xQueueSendToBack().
When entering tickless sleep, just before the call to portSUPPRESS_TICKS_AND_SLEEP() I see that vTaskSuspendAll() is called, and xTaskResumeAll() is called afterwards (from tasks.c). Looking at the documentation for vTaskSuspendAll(): “API functions that have the potential to cause a context switch (for example, vTaskDelayUntil(), xQueueSend(), etc.) must not be called while the scheduler is suspended.”
Based on this, is it safe to call the xQueueSendToBackFromISR() / xTimerStartFromISR() functions? I gather that they will not cause a context switch, but I am just hoping to clarify this to make sure there are no problems!