Summary: Implementing Hard RealTime Transactions on
James H. Anderson, Rohit Jain, and Srikanth Ramamurthy
Department of Computer Science, University of North Carolina at Chapel Hill
We present a new approach to implementing realtime transactions on memoryresident data on shared
memory multiprocessors. This approach allows hard deadlines to be supported without undue overhead.
In our approach, transactions are implemented by invoking waitfree library routines. Concurrency control
is embedded within these routines, so no special support for data management is required of the kernel or
from underlying server processes. These routines reduce the overhead involved in executing transactions by
exploiting the way transactions are interleaved on prioritybased realtime systems. We present evidence that
shows that our approach often entails substantially less overhead than more conventional priority inheritance
Many applications exist in which hard realtime transactions must be supported; examples include embed
ded control applications, defense systems, and avionics systems. With the recent advent of workstationclass
multiprocessor systems, multiprocessorbased implementations of these systems are of growing importance. Un
fortunately, the problem of implementing hard realtime transactions on multiprocessors has received relatively
\Lambda Work supported, in part, by NSF grants CCR 9216421 and CCR 9510156, and by a Young Investigator Award from the U.S.
Army Research Office, grant number DAAH049510323. The first author was also supported by an Alfred P. Sloan Research