13.07.2015 Views

5. Predavanje - VTS NS

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Upotreba semaforaŠta je problem sa sledećim kodom (S1 i S2 su inicijalno 1)?process P1;wait(S1);wait(S2);...signal(S2);signal(S1);end P1;Moguća sekvenca:P1 - wait(S1);P2 - wait(S2);P1 - wait(S2);P2 - wait(S1);// S1:=0// S2:=0// P1 blocks on S2// P2 blocks on S1process P2;wait(S2);wait(S1);...signal(S1);signal(S2);end P2;Problem - mrtvo (ili kružno) blokiranje (deadlock):stanje sistema u kome je nekoliko procesasuspendovano (blokirano) međusobnimuslovljavanjem (čekanjem) - detalji u OS279/285

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