Question

Semephore $1=1, s2-1; int a 0, 60; P20 { if(a > 0) { senwait(s2); senwait(s); } P1() { senwait(s); aH+; senwait(s2); bH+; sendignal (s2); senSignal(s1); else{ senwait(s1); senwait(s2); } b-- } --; senSignal(s); senSignal(s2);

will deadlock occurs or not why? explain
urgent

Answer 1

Suppose first process P1 is executing at starting S1=1 and S2=1

When semWait(S1) execute it makes S1=0;

After then when semWait(S2) execute it makes S2=0

Now suppose P1 gets Preempt and P2 get start to execute now when semWait(S1) try to execute but already S1=0 so process will get blocked same thing happened when semWait(S2) is executed.

So process P2 will get blocked hence there will be a deadlock.

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