Return to Home page

Differences

This shows you the differences between two versions of the page.

@@ Line 1: / Line 1: @@
+Return to [[os:|Operationg Systems home]]
+----
+====== Operating Systems Course: Lab08 ======
+===== Laboratory number 08 =====
+==== Exercise 01: Access to critical sections ====
+Suppose to have in substitution of the function ''test-and-set'' and of the function ''swap'', the following atomic function:
+<code c>
+int atomicIncrement (int *var) {
+  int tmp = *var;
+  *var = tmp + 1;
+  return (tmp);
+}
+</code>
+Use this function to write the functions ''init'', ''lock'', and ''unlock'' to insert in the //reservation code// and in the //release code// of a critical section.
+**Suggestion:**\\
+Use two global variables ''ticketNumber'' and ''turnNumber''.\\
+The first indicates the reservation order to enter the //critical section//, and the second manages the turn for accessing the critical section.\\
+Manage these variables through the functions ''init'', ''lock'', and ''unlock''.
+==== Exercise 02-04: Precedence graphs with semaphores ====
+Given the following //precedence graph//:
+<code txt>
+       A  <--------
+    /  |  \       ^
+   /   |   \      |
+  B    C    D     |
+  |   / \   |     |
+  |  /   \  |     |
+  | E    F  |     |
+  |  \   /  |     |
+  |   \ /   |     |
+  |    G    H     |
+   \   |   /      |
+    \  |  /       |
+       I  ---------
+</code>
+in which each vertex corresponds to an independent task (a process or a thread).\\
+Implement it with the following ways, and using the minimum number of semaphores.
+=== Exercise 02 ===
+Each task corresponds to a process.\\
+Each process is (re-)created and destroyed at each iteration of the principal cycle.\\
+Semaphores are implemented by means of pipes.
+=== Exercise 03 ===
+Each task corresponds to a thread.\\
+Each thread is (re-)created and destroyed at each iteration of the principal cycle.\\
+Semaphores are implemented by means of the POSIX library, and types/functions ''sem_*''.
+=== Exercise 04 ===
+Each task corresponds to a thread.\\
+Threads are all **cyclic** and they are created and destroyed only one time in the principal cycle.\\
+Semaphores are implemented by means of the POSIX library, and types/functions ''sem_*''.

If you found any error, or if you want to partecipate to the editing of this wiki, please contact: admin [at] skenz.it

You can reuse, distribute or modify the content of this page, but you must cite in any document (or webpage) this url: https://www.skenz.it/os/lab08?rev=1575529002&do=diff