Question 10251 – Operating-Systems

Consider the following program segment for concurrent processing using semaphore operators P and V for synchronization. Draw the precedence graph for the statements S1 to S9.

 var
 a, b, c, d, e, f, g, h, i, j, k : semaphore;
 begin
 cobegin
    begin S1; V(a); V(b) end;
    begin P(a); S2; V(c); V(d) end;
    begin P(c); S4; V(c) end; 
    begin P(d); S5; V(f) end;
    begin P(e); P(f); S7; V(k) end;
    begin P(b); S3;V(g);V(h) end;
    begin P(g); S6; V(i) end;
    begin P(h); P(i); S8; V(j) end;
    begin P(j); P(j); P(k); S9 end;
 coend
 end; 

Correct Answer: A