Computer Science 432/563
Operating Systems

Spring 2016, The College of Saint Rose

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All of the programs here are designated as practice programs for grading purposes.

You may work individually or with a partner on this lab assignment.

Running Class Examples

Run the class examples that used fork and POSIX threads in the following three environments to answer the questions that follow in a file answers.txt.

1. The Linux system mogul.strose.edu.
2. The FreeBSD system ascg.strose.edu.
3. The text's virtual Linux environment you set up as part of the first lab. (If you were unable to do this, there is a way to run it from the AH 400 suite Windows machines.)

The what_shared program when executed on my MacBook Pro (Mac OS X 10.9.5) is as follows:

First, we create two threads to see better what context they share...
Set this_is_global=1000
Thread 1, pid 75371, addresses: &global: 10C9DB050, &local: 10CA8FEDC
In Thread 1, incremented this_is_global=1001
Thread 2, pid 75371, addresses: &global: 10C9DB050, &local: 10CB12EDC
In Thread 2, incremented this_is_global=1002
After threads, this_is_global=1002

Now that the threads are done, let's call fork..
Before fork(), local_main=17, this_is_global=17
In parent, pid 75371: &global: 10C9DB050, &local: 7FFF53225538
In child, pid 75372: &global: 10C9DB050, &local: 7FFF53225538
Child set local_main=13, this_is_global=23
In parent, local_main=17, this_is_global=17

On my Mac, wthe proctree_threads program can create a thread tree of height 10 without encountering any thread creation errors, but did encounter errors at height 11.

fork() Practice

Notes:

• Do some error checking. If your program is run without a command-line argument, print a "Usage" line. If your program is given a negative starting value for the sequence, print an appropriate error message.
• If you store the entire sequence in an array as you generate it, allocate the array of an appropriately large size using malloc(3). Reminder to Java programmers: C has no garbage collection, so any memory you allocate with malloc() must be returned to the system with free().
• If you store the values in the sequence with int values, you will notice they could overflow the storage capabilities of the data type. You can delay this somewhat by using long values. Even then, you could overflow the values with certain starting values. In this case, also print an error message.

Adding POSIX Shared Memory

Once your program is working, add a call to sleep(2) (recall that "2" here refers to the manual section, not the argument to pass) to your program before you detach and free the shared memory segment. In a separate window, use the ipcs command to see that your shared memory segment is listed, and that it goes away when your program terminates. Save this output and include it in a file ipcs.out to be included in your submission.

Using POSIX Threads

Submission and Evaluation

This lab is graded out of 40 points.

To submit this lab, place all of the files that you are to turn in (and nothing else) into a directory called lab2, change to that directory, and create a "tar file" to submit using a command similar to:

tar cvf lab2.tar lab2

This will create a file lab2.tar in your directory. Send this tar file as an attachment to terescoj AT strose.edu by 11:59 PM, Wednesday, February 10, 2016.

Please include a meaningful subject line (something like "CS432 Lab 2 Submission") and use the exact filenames specified (for this lab and all semester) to make my job easier when gathering your submissions together for grading. You don't want to annoy your grader with misnamed or missing files just before he grades your assignment. Please do not include any additional files, such as emacs backup files, object files, or executable programs.