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Two processes, P1 and P2, need to access a critical section of code. Consider the following synchronization construct used by the processes:
Here, wants1 and wants2 are shared variables, which are initialized to false./* P1 */
while (true) {
wants1 = true;
while (wants2==true);
/* Critical
Section */
wants1=false;
}
/* Remainder section *//* P2 */
while (true) {
wants2 = true;
while (wants1==true);
/* Critical
Section */
Wants2=false;
}
/* Remainder section */
Which one of the following statements is TRUE about the above construct?
[2 marks]
(A) It does not ensure mutual exclusion.
(B) It does not ensure bounded waiting.
(C) It requires that processes enter the critical section in strict alternation.
(D) It does not prevent deadlocks, but ensures mutual exclusion.
asked in Computer Science And Engineering, 2007
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274.
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276.
An operating system uses Shortest Remaining Time first (SRT) process scheduling algorithm. Consider the arrival times and execution times for the following processes:
What is the total waiting time for process P2? [2 marks]Process Execution time Arrival time P1 20 0 P2 25 15 P3 10 30 P4 15 45
(A) 5
(B) 15
(C) 40
(D) 55
asked in Computer Science And Engineering, 2007
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