Simplified Arbiter as an example

COMPONENT arbiter(reql, grl, reqr, grr: BOOLEAN)

INITIALLY grl = FALSE grr = FALSE

<< reql ? ?grr ? grl:= TRUE>> ||

<< ? reql ? grl ? grl:= FALSE>> ||

<< reqr ? ?grl ? grr:= TRUE>> ||

<< ? reqr ? grr ? grr:= FALSE>>

END arbiter

Would check grr and grl are never both true. This is mutual exclusion, to beasserted, ? (grl ? grr).

Reading assignment: Section 6.5.1 of Text

Arbiter

Client

Left

Client

Right

reql

grl grr

reqr

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