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Synchronization Mechanisms

Lock variable ("mutex")

mutex lock = INIT();
P: loop             C: loop
     v = produce()       LOCK(lock)
     LOCK(lock)          C2
     C1                  UNLOCK(lock)
     UNLOCK(lock)        consume(v)

• Shared variable
• States: "locked" and "unlocked"
• If locked, LOCK() blocks until unlocked.

Only one process can have lock => only one process can enter critical region!