Monitors

• Semaphores are a pain - so alternative? - Monitors
• Implemented with explicit calls to locks and condition variables (not exactly a programming language construct as Tenenbaum says)
• Used in WinNT, OS/2, Solaris and other OS's
• Used to obtain mutual exclusion and busy wait
• Locks : see them before (acquire before using a resource, and then release)
• Condition Variables : variables describing state of a resource (full, empty etc)
• Operations on condition variables : Wait (release lock), Signal (wake up a waiting process) and Broadcast (wake up all waiting processes)