Process scheduling
- 1. 1 Process Synchronization (Galvin) Outline CHAPTER OBJECTIVES To introduce the critical-section problem, whose solutions can be used to ensure the consistency of shared data. To present both software and hardware solutions of the critical-section problem. To examine several classical process-synchronization problems. To explore several tools that are used to solve process synchronization problems. BACKGROUND THE CRITICAL SECTION PROBLEM PETERSON'S SOLUTION SYNCHRONIZATION HARDWARE MUTEX LOCKS SEMAPHORES o Semaphore Usage o Semaphore Implementation o Deadlocks and Starvation o Priority Inversion CLASSIC PROBLEMS OF SYNCHRONIZATION o The Bounded-Buffer Problem o The Readers–Writers Problem o The Dining-Philosophers Problem MONITORS o Monitor Usage o Dining-Philosophers Solution o Using Monitors o Implementing a Monitor o Using Semaphores o Resuming Processes within a Monitor SYNCHRONIZATION EXAMPLES o Synchronization in Windows o Synchronization in Linux o Synchronization in Solaris o Pthreads Synchronization ALTERNATIVE APPROACHES o Transactional Memory o OpenMP o Functional Programming Languages Contents A cooperating process is one that canaffect or be affectedbyother processes executing inthe system. Cooperating processescaneither directlyshare a logical address space (that is, both code anddata)or be allowed to share data onlythroughfiles or messages. The former case is achievedthroughthe use of threads, discussedinChapter 4. Concurrent accessto shareddata mayresult in data inconsistency, however. Inthis chapter, we discussvarious mechanisms to ensure the orderlyexecution ofcooperating processesthat share a logical address space, sothat data consistencyis maintained. BACKGROUND We’ve alreadyseen that processes canexecute concurrentlyor in parallel. Section 3.2.2 introducedthe role of processsched ulingand described how the CPU scheduler switches rapidlybetween processesto provide concurrent execution. This means that one process may onlypartiallycomplete execution before another processis scheduled. Infact, a process maybe interruptedat anypoint in its instruction
- 2. 2 Process Synchronization (Galvin) stream, andthe processing core maybe assigned to execute instructions of another process. Additionally, Section4.2 introducedparallel execution, in whichtwo instruction streams (representing different processes) execute simultaneouslyon separate processing cores. Inthis chapter, we explain how concurrent or parallelexecutioncan contribute to issues involving the integrityof data sharedbyseveral processes. AssortedContent XXX To be cleared I Q’s Later XXX Glossary ReadLater Further Reading S Grey Areas XXX