1. A method of managing memory in a computer system, said method comprising: setting a first bit of an indicator associated with a cache line in a cache memory if said cache line has been accessed in response to a processor executing an instruction in a first group of instructions; setting a second bit of said indicator while said first bit remains set if said cache line has also been accessed in response to said processor executing an instruction in a second group of instructions; executing a third group of instructions that causes said cache line to be accessed, wherein said third group of instructions is executed by an agent other than said processor, wherein said processing comprises rolling back said first group of instructions provided said first bit is set and rolling back said second group of instructions provided said second bit is set before allowing an instruction in said third group to access said cache line, and otherwise granting said access; and processing said first group and said second group of instructions according to a value of said indicator.