From: Honghai Liu (liu789_at_hotmail.com)
Date: Mon Jan 12 2004 - 14:14:30 PST
Reviewer: Honghai Liu
The paper discussed on protection mechanisms under a parallel computing environment, as demonstrated by MCS system.
To me, the most important aspect of the paper is that thorough analysis and discussion on capacity list. Even though the Access Control List protection model, which was introduced by Multics system, might be more popular to the network administration users, the alternative, capacity list, offers some distinctive features that provide more flexibility and controls in many ways. The paper provided many protection mechanisms along with interesting examples, showing how powerful the C-list can be. Besides traditional capacities, i.e. segment and i/o function of X/R/W, the author provides a lot of facilities to describe the usage of the C-list on other entities
1)inter-process: Inferior Sphere of protection details on how the superior computation create inferior computation with the proper control of capacity.
2)procedure: Protected Entry Points makes sure that a restricted use of a procedure under the C-list.
3)directory: The creation, acquire, release, remove are the meta-instructions to be used to take the advantage of C-list on directories.
Some other interesting ideas:
1) Computation is composed of a set of process, and they have a common C-list. Even though I cannot think of a corresponding contemporary term ( perhaps there is a one), the concept of a set of processes running the same capacity indeed exists.
2) Several primitive operations of parallel programming are given and to show how people about 40 years ago offered synchronizations before semaphore was created. It was not surprising that the meta-instructions, or through the support from the CPU hardware, is the easiest way to achieve.
3) Several issues (such as Ambiguous, Flase etc.) related to naming was carefully discussed, followed by the solution that a partial name to some directory of objects with index number of a capability pointing to that directory.
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