School of Computing and Information Systems
COMP30023: Computer Systems
Tutorial Week 3
Process lifetime, scheduling, interprocess communication and threads
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1. In the lectures, a multi-threaded text editor was shown. If the only way to read from a file is the normal blocking read system call, do you think user-level threads or kernel-level threads are being used for the text editor? Why?
2. What is a race condition? What is a deadlock?
3. In the lectures we saw that the priority inversion problem can happen with processes. Can the priority inversion problem happen with user-level threads? Why or why not?
4. In lectures we saw a concept of a resource graph and a circular chain that leads to a deadlock. Give an example to show that the set of processes deadlocked can include processes that are not in a circular chain in the cor- responding resource allocation graph. Recall that processes and resources are represented as nodes and there is a directed edge from a process to a resource that it needs to acquire and an edge from a resource to a process that indicated that this process has acquired this resource.
5. Can a measure of whether a process is likely to be CPU bound or I/O bound be determined by analysing source code? How can this be deter- mined at run time?
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Weekly tutorial participation activity
To obtain a weekly tutorial mark (1% of your overall mark for the subject, totalling to 10% over the semester), please answer the following questions in Canvas Quiz (called Week 3 Tutorial Activity). You can have multiple attempts but need to submit the quiz by 11:59 pm AEDT on the day of your tutorial. Only answering all questions correctly will give you the week¡¯s mark.
During the tutorial, your tutor will provide you with the access code that will unlock the quiz for the corresponding week. The access code is valid only for students in this tutorial. As a result, we expect you to attend your tutorial class as otherwise the access code you obtain in another tutorial will not work for you.
If you have a valid reason for not being able to attend your tutorial, please fill in the form accessible via Canvas by Friday 8pm AEDT of the corresponding week. You will be given an access code during the next business day. The code will not be provided otherwise, hence, please do not email the subject coordinator or other staff members including your tutor asking for the code. We will monitor such requests and may limit the number of times an access code is given to the same student throughout the semester to encourage participation and attendance of the tutorials.
1. Consider the following piece of C code:
void main( ) {
exit( ); }
How many child processes are created upon execution?
(a) 0 (b) 1 (c) 2 (d) 3 (e) 4
2. Choose objects that are shared between threads (Multiple answer ques- tion):
(a) Program code (b) Global variables
(c) Local variables
(d) Dynamically allocated memory (e) Registers
3. Select the number of processes that can be deadlocked with each other (Multiple answer question):
(a) 2 (b) 3 (c) 4
(d) Any number involving more than 2 processes
4. Suppose a scheduling algorithm operates as follows. If a new process gets created while another process is running, the scheduler suspends it and gives priority to the new process by allocating it to the CPU. This scheduling algorithm is preemptive.
(a) True (b) False
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