Consider a system with the following resource profile:
Resource Type Number of Instances
RT1 2
RT2 2
RT3 1
RT4 1
RT5 1Let REQ(A, B) denote process A's request for a resource of type B. Let the system execute the following sequence of requests:
REQ(P7, RT3)
REQ(P2, RT4)
REQ(P3, RT2)
REQ(P6, RT5)
REQ(P5, RT1)
REQ(P3, RT4)
REQ(P4, RT1)
REQ(P1, RT2)
REQ(P4, RT5)
REQ(P1, RT4)
REQ(P6, RT1)
At the end of processing the above sequence of resource requests, there is no deadlock in the system. We can verify this fact by constructing the resource-allocation graph and analyzing the cycles in the graph. Specifically, the cycle P4→RT5→P6→RT1→P4 does not imply a deadlock, because there is a second resource of type RT1 held by P5. Since P5 is free to proceed, it can eventually release its resource of type RT1, which allows P6, and eventually P4, to proceed.
Now, consider each of the following requests and examine if it causes a deadlock. Identify the request that will cause a deadlock in the system?
A. REQ(P2, RT5)
B. REQ(P2, RT3)
C. REQ(P2, RT1)
D. REQ(P2, RT2)