V. V. Nikiforov - Dr.Sc. (Eng.), Professor, Leading Research Scientist, St. Petersburg Institute for Informatics and Automation of the Russian Academy of Sciences (SPIIRAS). E-mail: nik@iias.spb.ru

The order of access to mutual resources in multi-task systems shall guarantee impossibility of task deadlocks. The necessary condition of deadlocks is the presence of intersected critical intervals for access to mutual resources. That is why the special protocols for access to mutual resources are used for implementation of software applications with intersected critical intervals - the protocols, which prevent the possibility of deadlocks. The known protocols of such kind shall be used with scheduling modes with static priorities, more efficient scheduling modes can-t co-exist with these protocols. However, the presence of intersected critical intervals is only necessary, but not sufficient for possibility of deadlock occurrence, i.e. the use of special protocol may be idle. The paper suggests a criteria, that permits to check the necessity of special protocol usage; the checking is performed by static analysis of the task interactions structure. If the analysis shows, that the special protocol is not needed, than the system may be work with any efficient scheduling mode.