Operating Systems Multiprocessor Synchronization 1) CPU 1 Word 1000is Memory CPU 2 initially o 1. CPU 1 reads a O 2. CPU 2 reads a O 3. CPU 1 writes a 1 4. CPU 2 writes a 1 Bus g tSL instruction can fail if the bus cannot be locked G To prevent this problem, the TSL instruction must first lock the bus, preventing other CPUs from accessing it then do both memory accesses, then unblock the bus Gao Haichang, Software School, Xidian University 17Operating Systems Gao Haichang , Software School, Xidian University 17 Multiprocessor Synchronization (1) TSL instruction can fail if the bus cannot be locked To prevent this problem, the TSL instruction must first lock the bus, preventing other CPUs from accessing it, then do both memory accesses, then unblock the bus