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%T Combining EDF Scheduling with occam using the Toc Programming Language
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%A Martin Korsgaard, Sverre Hendseth
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%E Peter H. Welch, S. Stepney, F.A.C Polack, Frederick R. M. Barnes, Alistair A. McEwan, G. S. Stiles, Jan F. Broenink, Adam T. Sampson
%B Communicating Process Architectures 2008
%X A special feature of the occam programming language is that
its
concurrency support is at the very base of the language.
However, its
ability to specify scheduling requirements is
insufficient for use in
some real\-time systems. Toc is an
experimental programming language
that builds on occam,
keeping occam\[rs]s concurrency mechanisms,
while
fundamentally changing its concept of time. In Toc,
deadlines are
specified directly in code, replacing
occam\[rs]s priority constructs as
themethod for controlling
scheduling. Processes are scheduled lazily,
in that code is
not executed without an associated deadline. The
deadlines
propagate through channel communications, which means
that a
task blocked by a channel that is not ready will
transfer
its deadline through the channel to the dependent
task. This allows
the deadlines of dependent tasks to be
inferred, and also creates
a scheduling effect similar to
priority inheritance. A compiler and
run\-time system has
been implemented to demonstrate these principles.