Question

Question # 4: People have said that proper spooling would have eliminate deadlocks. Certainly, it eliminates from contention card readers, plotters, printers, and so on. It is even possible to spool tapes (called staging them), which would leave the resources of CPU time, memory and disk space. Is it possible to have a deadlock involving these resources? If it is not, why not? W5hat deadlock scheme would seem best to eliminate these deadlocks (if any are possible) or what condition is violated (if they are not possible)?

Answer 1

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when no failure occurs?

\ufffd The time it takes to recover from a system crash?

\ufffd The time it takes to recover from a disk crash?

Answer: No answer.

7.22 Explain the concept of transaction atomicity.

Answer: No answer.

7.23 Show that the two-phase locking protocol ensures conflict serializability.

Answer: No answer.

7.24 Show that some schedules are possible under the two-phase locking proto-

col but not possible under the timestamp protocol, and vice versa.

Answer: No answer.

Chapter 8

DEADLOCKS

Deadlock is a problem that can only arise in a system with multiple active asynchronous pro-

cesses. It is important that the students learn the three basic approaches to deadlock: prevention,

avoidance, and detection (although the terms prevention and avoidance are easy to confuse).

It can be useful to pose a deadlock problem in human terms and ask why human systems

never deadlock. Can the students transfer this understanding of human systems to computer

systems?

Projects can involve simulation: create a list of jobs consisting of requests and releases of

resources (single type or multiple types). Ask the students to allocate the resources to prevent

deadlock. This basically involves programming the Banker\u2019s Algorithm.

The survey paper by Coffman, Elphick, and Shoshani [1971] is good supplemental reading,

but you might also consider having the students go back to the papers by Havender [1968],

Habermann [1969], and Holt [1971a]. The last two were published in CACM and so should be

readily available.