13.07.2015 Views

5. Predavanje - VTS NS

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Međusobno isključenjePrimer 1: Šta se dešava ako dva procesa pristupaju uporedo istojdeljenoj promenljivoj x?x:=x+1Na većini procesora, ova naredba biće prevedena u (neatomičnu)sekvencu (atomičnih) instrukcija:load reg with xincrement regstore reg to xAko je x incijalno bilo 0, koji su mogući rezultati?Slučaj 1: Slučaj 2: ...P1 P2 P1 P2load x(0)load x(0)load x(0)incinc inc store x(1)store x(1)load x(0)store x(1) ...x=1 x=245/285

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