Method an apparatus for tolerance of lost timer ticks during recovery of

Abstract

A method and apparatus for detecting and tolerating situations in which one or more processors in a multi-processor system cannot participate in timer-driven or timer-triggered protocols or event sequences. The multi-processor system includes multiple processors each having a respective memory. These processors are coupled by an inter-processor communication network (preferably consisting of redundant paths). Processors are suspected of having failed (ceased operations) outright or having a failed timer mechanism when other processors detect the absence of periodic 'IamAlive' messages from other processors. When this happens, all of the processors in the system are subjected to a series of stages in which they repeatedly broadcast their status and their connectivity to each other. During the first such stage, according to the present invention, a processor will not assert its ability to participate unless its timer mechanism is working. It arms a timer expiration event and does not assert its health until and unless that timer expiration event occurs.