COMS 414 - Prelim 1 Review SessionPrelim 1Before we begin …MultitaskingSlide 5SynchronizationSlide 7Vivek Presents …MonitorsSynchronization ProblemsDeadlockDeadlocksSlide 13Deadlock PreventionDeadlock AvoidanceCOMS 414 - Prelim 1 Review SessionMultiprocessing and SynchronizationSunny([email protected]) Vivek([email protected])Prelim 1•There are many, many resources available for your Prelim 1 needs: (presented in random order)–Your notes!–The book and its website–FA2000 Homeworks/Solutions–FA2000 Prelim 1 review slides–SP2001 Lecture notes–Newsgroup–Plenty of office hours!–Additional support by appointmentBefore we begin …•Any questions from the CS314 review session?–Register set, stack, heap–Program counter–Interrupts / exceptions–Interrupt priority levels–Programmable I/O vs. DMA–Polling–Memory protection (base/limit)Multitasking•What is a:–Process or Task?–Thread?•What is the difference between a program and a process?•What is in the PCB?•Differences between O/S processes and user processes?•Differences between user-level threads and kernel-level threads?Multitasking•What is kernel space?•What is user space?•What is a system call?•What is a context switch?•What states may a process be in?•How do processes go between states?•What is a race condition?Synchronization•What is a critical section?•What are the three requirements for protection of a critical section?•What is busy waiting?•What are atomic instructions?•What is a semaphore?Synchronization•Three levels of abstraction for concurrent programming:–Hardware instructions–O/S functions–Programming language constructsVivek Presents …•Classic Synchronization Problems•Monitors, Condition Variables and Language Support•Deadlocks, Prevention and AvoidanceMonitors•What is a monitor?•What are condition variables?•Differentiate between semaphores and condition variables.Synchronization Problems•Bounded buffer problem•Readers writers problem•Dining philosophers problemsDeadlock•What is a deadlock?•Necessary conditions for deadlock ?Deadlocks R1 R2....P1 P2P3R3Deadlocks.....P1 P2P3R3P4 R1 R2Deadlock Prevention Make sure that one of the necessary conditions does not hold -- Mutual exclusion -- Hold and Wait -- No Pre Emption -- Circular WaitDeadlock Avoidance•What is it?•What is Safe State?•Safety Check?•Bankers
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