Currenty it is not valid to set configMAX_SYSCALL_INTERRUPT_PRIORITY to 0 (highest prority).
This is because of the way the port masks isr's. ( Using the basepri register, which is disabled with a 0 value ).
The port can be improved with some #if ( configMAX_SYSCALL_INTERRUPT_PRIORITY == 0 ) magic to use different asm in this configuration to instead disable/enable isr's and apropriate exceptions.
Darren Jenkins ( darrenjenkins ) - 2012-05-23 00:12:23 PDT