1 research outputs found
Safe Register Token Transfer in a Ring
A token ring is an arrangement of N processors that take turns engaging in an
activity which must be controlled. A token confers the right to engage in the
controlled activity. Processors communicate with neighbors in the ring to
obtain and release a token. The communication mechanism investigated in this
paper is the safe register abstraction, which may arbitrarily corrupt a value
that a processor reads when the operation reading a register is concurrent with
an write operation on that register by a neighboring processor. The main
results are simple protocols for quasi-atomic communication, constructed from
safe registers. A quasi-atomic register behaves atomically except that a
special undefined value may be returned in the case of concurrent read and
write operations. Under certain conditions that constrain the number of writes
and registers, quasi-atomic protocols are adequate substitutes for atomic
protocols. The paper demonstrates how quasi-atomic protocols can be used to
implement a self-stabilizing token ring, either by using two safe registers
between neighboring processors or by using O(lg N) safe registers between
neighbors, which lowers read complexity.Comment: 22 page