Synchronization with Eventcounts and Sequencers

Synchronization of concurrent processes requires controlling the relative 
ordering of events in the processes.
A new synchronization mechanism is proposed, using 
abstract objects called eventcounts and sequencers, that allows processes
to control the ordering of events directly, rather than using mutual
exclusion to protect manipulations of shared variables that control
ordering of events.  Direct control of ordering seems to simplify
correctness arguments and also simplifies implementation in distributed
systems.  The mechanism is defined formally, and then several
examples of its use are given.  The relationship of the mechanism
to protection mechanisms in the system is explained; in particular,
eventcounts are shown to be applicable to situations where confinement
of information matters.  An implementation of eventcount
s and sequencers in a system with shared memory is described.

CACM February, 1979

Reed, D.
Kanodia, R.

Process synchronization, interprocess communication, distributed
systems, security models, mutual exclusion, semaphores

4.30 4.32

CA790207 DH April 12, 1979  10:03 AM

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