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-- blm
This is a second test of my cs4320 mailing list, and also a suggestion that any of you with free time this weekend start reading chapter 1 of the textbook.
-- blm
The 10 students present for the 9:55am section voted unanimously to go back to watching the news rather than discuss operating systems, understandably. I'll be in HAS 228 at 11:20am, ready to talk about course material if at least half the students are present and willing, but I think today we may all find it too difficult to concentrate.
I had planned to be out of town for Thursday's class, but that's looking unlikely. If you don't hear from me, assume we *will* have class; if I do cancel class, I'll let you know by e-mail as soon as possible.
-- blm
One student asked about question 6, so let me clarify for everyone: What I'm asking for is a sketch of how to implement the semaphore operations up() and down(), given that you have a single-CPU system on which the o/s can disable interrupts. (In class we talked about how to implement these operations if you have a TSL instruction and possibly more than one CPU.)
-- blm
Most people were either in favor of or neutral about changing the exam date, so: We'll have exam 1 next Thursday (Oct. 18), not Tuesday as it says in the syllabus. That will allow me to at least distribute a solution to Homework 2 (due Tuesday) before the exam. Note that the exam will be open book, which I hope will reduce the amount of time you need to spend preparing for it.
-- blm
Homework 2 is due next Tuesday (October 16) at 5pm. I plan to make a sample solution available then, so I won't accept late work for this assignment. I also plan to make available a sample solution for Homework 1, probably tomorrow. FYI.
-- blm
I've posted a short review sheet describing Thursday's exam, linked from http://www.cs.trinity.edu/~bmassing/CS4320_2001fall/assignments.html. I will also make available a sample solution for Homework 2 tomorrow (Wednesday), probably in hardcopy format available from me or from Nicole in the department office.
-- blm
In grading the homeworks I've come up with the following clarifications, additions, etc., to the homework solutions I distributed earlier:
(*) Homework 1, Question 4: Criterion (4) is, in my opinion, ambiguous: If it means that every process gets to enter its critical region at least once, then it is satisfied, since the problem described for (3) can only occur after each process has gone through its critical region at least once. If it means that a process never has to wait forever to enter its critical region, then it is not satisfied, for the same reasons (3) is not satisfied.
(*) Homework 2, Question 2: It's worth noting that if one uses this scheme to add a notion of priorities to round-robin scheduling, one would need to be careful to remove from the list of runnable processes all entries for a process that has ended or is blocked. It's also worth noting that in my answer, I'm assuming that the list of runnable process consists of pointers to process blocks, or process IDs, or something else that we can easily duplicate *without* duplicating the actual process block -- if we duplicate the process block, we essentially have two separate processes, which doesn't really make sense.
-- blm
An alert student has just brought to my attention an error in question 7: 64 is not 2^8 (2 to the 8th power) but 2^6. I've corrected the assignment online; please take this correction into account in answering this question. Also, for the two questions asking about the size of a page table, you should express the size of each entry in bytes (not bits), assuming 8 bits per byte and rounding up if necessary (so, for example, if each entry required 6 bits, you would round up to one byte).
-- blm
I've posted a short review sheet describing the second exam, linked from http://www.cs.trinity.edu/~bmassing/CS4320_2001fall/assignments.html. I will also return Homework 3 and distribute a solution. Solutions for Homeworks 4 and 5 will be available tomorrow or Monday.
-- blm