1
GATE CSE 2006
MCQ (Single Correct Answer)
+2
-0.6
The atomic fetch-and-set x, y instruction unconditionally sets the memory location x to 1 and fetches the old value of x n y without allowing any intervening access to the memory location x. consider the following implementation of P and V functions on a binary semaphore S.
void P (binary_semaphore *s) {
unsigned y;
unsigned *x = &(s->value);
do {
fetch-and-set x, y;
} while (y);
}
void V (binary_semaphore *s) {
S->value = 0;
}
Which one of the following is true? 2
GATE CSE 2003
MCQ (Single Correct Answer)
+2
-0.6
Suppose we want to synchronize two concurrent processes P and Q using binary semaphores S and T. The code for the processes P and Q is shown below.
Process P:
Process Q:
Process P:
while(1){
W:
Print '0';
Print '0';
X:
}
Process Q:
while(1){
Y:
Print '1';
Print '1';
Z:
}
Synchronization statements can be inserted only at points W, X, Y, and Z.Which of the following will ensure that the output string never contains a substring of the form 01n0 or 10n1 where n is odd?
3
GATE CSE 2003
MCQ (Single Correct Answer)
+2
-0.6
Suppose we want to synchronize two concurrent processes P and Q using binary semaphores S and T. The code for the processes P and Q is shown below.
Process P:
Process Q:
Process P:
while(1){
W:
Print '0';
Print '0';
X:
}
Process Q:
while(1){
Y:
Print '1';
Print '1';
Z:
}
Synchronization statements can be inserted only at points W, X, Y, and Z.Which of the following will always lead to an output starting with 001100110011
4
GATE CSE 2001
MCQ (Single Correct Answer)
+2
-0.6
Consider Peterson’s algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below.
Repeat
flag[i]=true;
turn=j;
while (P) do no-op;
Enter critical section, perform actions, then
exit critical section
Flag[i]=false;
Perform other non-critical section actions.
Until false;
For the program to guarantee mutual exclusion, the predicate P in the while loop should be Questions Asked from Synchronization and Concurrency (Marks 2)
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