Abstract.   The protocols for software tasks access to joint resources are considered. А comparison is carried out of properties of such protocols in systems with single-core and multi-core processors. It is shown that some protocol properties, which are true for the systems with single-core processors, become invalid for the systems with multi-core processors. Both versions of the priority ceiling protocol prevent mutual blocking of tasks in systems with single-core processors, but stack-optimized version of the protocol loses this valuable property in systems with multi-core processors. Both versions of the protocol prevent composite blocking of tasks for single-core processors, but lose this property for multi-core processors.

Keywords:   multitask systems, systems with multi-core processors, real-time systems, cooperative tasks, protocols for access to resources