Consider the following code snippet using the fork()
and wait()
system calls. Assume that the code compiles and runs correctly, and that the system calls run successfully without any errors.
int x = 3;
while(x > 0) {
fork();
printf("hello");
wait(NULL);
x--;
}
The total number of times the printf
statement is executed is _______
Consider the two functions incr and decr shown below.
incr() {
wait(s);
X = X+1;
signal(s);
}
decr() {
wait(s);
X = X-1;
signal(s);
}
There are 5 threads each invoking incr once, and 3 threads each invoking decr once, on the same shared variable X. The initial value of X is 10.
Suppose there are two implementations of the semaphore s, as follows:
I-1: s is a binary semaphore initialized to 1.
I-2: s is a counting semaphore initialized to 2.
Let V1, V2 be the values of X at the end of execution of all the threads with implementations I-1, I-2, respectively.
Which one of the following choices corresponds to the minimum possible values of V1, V2, respectively?
![GATE CSE 2020 Operating Systems - Synchronization and Concurrency Question 5 English](https://imagex.cdn.examgoal.net/1da9i2ynkcu1mvih/fe1746d6-445a-4576-abb4-3fd25115a170/559ebf90-ca46-11ea-b796-4745b429ed6f/file-1da9i2ynkcu1mvii-320w.png)
What does the code achieve?