I'm using FreeRTOS v9.0.0 on a SAMV71 board. Things are working fine without the MPU enabled. However when I enable the MPU on the chip, with sensible defaults for the various memory regions (as set by Atmel's software framework), then I get the Dummy interrupt handler firing as soon as the scheduler starts (I'm guessing this should really be the timer interrupt).
I noticed there are some MPU extensions to FreeRTOS, but only the M3/M4 are explicitly mentioned. For the moment I don't expect to use the restricted task features. The reason I want to enable the MPU is to be able to selectively enable/disable caching for different regions of memory. (At the moment I need to disable caching entirely in order to support ethernet).
Probably there is something simple I'm missing. Is this supported by FreeRTOS?
There was indeed something I was missing - I had omitted a line from the linker script and so the variables not to be cached were being placed who knows where. That's why the dummy handler went off, it was a memory management fault; no errors occurred without the MPU enabled, but it turns out it wasn't working properly either as a result of the omission. So, nevermind. FreeRTOS is working fine with the MPU enabled.
Thanks for taking the time to report back.