A conditional abortable priority ceiling protocol for scheduling mixed real-time tasks

Priority Ceiling Protocol (PCP) is a well-known resource access protocol fo r hard real-time systems. However, it has a problem of ceiling blocking whi ch imposes a great hindrance to task scheduling in mixed real-time systems where tasks may have different criticality. In this paper, a new resource a ccess protocol called the Conditional Abortable Priority Ceiling Protocol ( CA-PCP) is proposed. It resolves the problem of ceiling blocking by incorpo rating a conditional abort scheme into the PCP, The new protocol inherits a ll the desirable properties of the PCP and the Ceiling Abort Protocol (CAP) which is yet another modification of the PCP. In the proposed protocol, a condition is defined to control the abort of a job so that the schedulabili ty of the system will not be affected. Performance study has been done to c ompare the CA-PCP with the PCP. The results indicate that CA-PCP can signif icantly improve the performance of a system if the lengths of the abortable critical sections are well chosen. (C) 1999 Elsevier Science B.V. All righ ts reserved.