5. Multiprocessor

For OSes that clearly include the notion of task, i.e. the two "multitasking" cases we have just presented, we can add a multiprocessor dimension. Indeed, a survey [4] carried out in 2006 showed that 80% of embedded systems included at least two processors, and ITRS [5] predicts an explosion in the number of processors. This is a new situation that operating systems for embedded systems must take into account.

The strategy for managing the different processors varies according to the hardware architecture in question.

For homogeneous architectures, i.e. with a single type of processor and a regular memory architecture, we generally opt for a "symmetric" operating system (SMP or Symmetric Multiprocessing). In this situation, a single OS is used by all processors. At boot time, all processors load their instructions from the same address,...