book

PThreads Programming

by Dick Buttlar, Jacqueline Farrell, Bradford Nichols

September 1996

Intermediate to advanced

286 pages

7h 11m

English

O'Reilly Media, Inc.

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Pthreads Programming
A Note Regarding Supplemental Files
Examples
Preface
OrganizationExample ProgramsFTPTypographical ConventionsAcknowledgments
1. Why Threads?
What Are Pthreads?Potential ParallelismSpecifying Potential Parallelism in a Concurrent Programming EnvironmentUNIX Concurrent Programming: Multiple ProcessesCreating a new process: forkPthreads Concurrent Programming: Multiple ThreadsCreating a new thread: pthread_createThreads are peersParallel vs. Concurrent ProgrammingSynchronizationSharing Process ResourcesCommunicationSchedulingWho Am I? Who Are You?Terminating Thread ExecutionExit Status and Return ValuesPthreads Library Calls and ErrorsWhy Use Threads Over Processes?A Structured Programming EnvironmentChoosing Which Applications to Thread
2. Designing Threaded Programs
Suitable Tasks for ThreadingModelsBoss/Worker ModelPeer ModelPipeline ModelBuffering Data Between ThreadsSome Common ProblemsPerformanceExample: An ATM ServerThe Serial ATM ServerHandling asynchronous events: blocking with selectHandling file I/O: blocking with read/writeThe Multithreaded ATM ServerModel: boss/worker modelThe boss threadDynamically detaching a threadA worker threadSynchronization: what’s neededFuture enhancementsExample: A Matrix Multiplication ProgramThe Serial Matrix-Multiply ProgramThe Multithreaded Matrix-Multiply ProgramPassing data to a new threadSynchronization in the matrix-multiply program
3. Synchronizing Pthreads
Selecting the Right Synchronization ToolMutex VariablesUsing MutexesError Detection and Return ValuesUsing pthread_mutex_trylockWhen Other Tools Are BetterSome Shortcomings of MutexesContention for a MutexExample: Using Mutexes in a Linked ListComplex Data Structures and Lock GranularityRequirements and Goals for SynchronizationAccess Patterns and GranularityLocking HierarchiesSharing a Mutex Among ProcessesCondition VariablesUsing a Mutex with a Condition VariableWhen Many Threads Are WaitingChecking the Condition on Wake Up: Spurious Wake UpsCondition Variable AttributesCondition Variables and UNIX SignalsCondition Variables and CancellationReader/Writer LocksSynchronization in the ATM ServerSynchronizing Access to Account DataLimiting the Number of Worker ThreadsSynchronizing a Server ShutdownThread PoolsAn ATM Server Example That Uses a Thread PoolInitializing a thread poolChecking for workAdding workDeleting a thread poolAdapting the atm_server_init and main routines
4. Managing Pthreads
Setting Thread AttributesSetting a Thread’s Stack SizeSpecifying the Location of a Thread’s StackSetting a Thread’s Detached StateSetting Multiple AttributesDestroying a Thread Attribute ObjectThe pthread_once MechanismExample: The ATM Server’s Communication ModuleUsing a statically initialized mutexUsing the pthread_once mechanismKeys: Using Thread-Specific DataInitializing a Key: pthread_key_createAssociating Data with a KeyRetrieving Data from a KeyDestructorsCancellationThe Complication with CancellationCancelability Types and StatesCancellation Points: More on Deferred CancellationA Simple Cancellation ExampleThe bullet_proof thread: no effectThe ask_for_it thread: deferred cancellationThe sitting_duck thread: asynchronous cancellationCleanup StacksCancellation in the ATM ServerAborting a depositScheduling PthreadsScheduling Priority and PolicyScheduling Scope and Allocation DomainsRunnable and Blocked ThreadsScheduling PriorityScheduling PolicyUsing Priorities and PoliciesSetting Scheduling Policy and PriorityInheritanceScheduling in the ATM ServerMutex Scheduling AttributesPriority CeilingPriority InheritanceThe ATM Example and Priority Inversion
5. Pthreads and UNIX
Threads and SignalsTraditional Signal ProcessingSending signals and waiting for signalsUsing a signal mask to block signalsSignal Processing in a Multithreaded WorldSynchronously generated signalsAsynchronously generated signalsPer-thread signal masksPer-process signal actionsPutting it all togetherThreads in Signal HandlersA Simple ExampleSome Signal IssuesHandling Signals in the ATM ExampleThreadsafe Library Functions and System CallsThreadsafe and Reentrant FunctionsExample of Thread-Unsafe and Threadsafe Versions of the Same FunctionFunctions That Return Pointers to Static DataLibrary Use of errnoThe Pthreads Standard Specifies Which Functions Must Be ThreadsafeAlternative interfaces for functions that return static dataAdditional routines for performance considerationsFile-locking functions for threadsWhere are the threadsafe functions?Using Thread-Unsafe Functions in a Multithreaded ProgramCancellation-Safe Library Functions and System CallsAsynchronous Cancellation-Safe FunctionsCancellation Points in System and Library CallsThread-Blocking Library Functions and System CallsThreads and Process ManagementCalling fork from a ThreadFork-handling stacksCalling exec from a ThreadProcess Exit and ThreadsMultiprocessor Memory Synchronization
6. Practical Considerations
Understanding Pthreads ImplementationTwo WorldsTwo Kinds of ThreadsWho’s Providing the Thread?User-space Pthreads implementationsKernel thread–based Pthreads implementationsTwo-level scheduler Pthreads implementations: the best of both worldsDebuggingDeadlockRace ConditionsEvent OrderingLess Is BetterTrace StatementsDebugger Support for ThreadsExample: Debugging the ATM ServerDebugging a deadlock caused by a missing unlockDebugging a race condition caused by a missing lockPerformanceThe Costs of Sharing Too Much—LockingThread OverheadThread context switchesSynchronization OverheadHow Do Your Threads Spend Their Time?Performance in the ATM Server ExamplePerformance depends on input workload: increasing clients and contentionPerformance depends on a good locking strategyPerformance depends on the type of work threads doKey performance issues between using threads and using processesConclusion

A. Pthreads and DCE
The Structure of a DCE ServerWhat Does the DCE Programmer Have to Do?Example: The ATM as a DCE Server
B. Pthreads Draft 4 vs. the Final Standard
Detaching a ThreadMutex VariablesCondition VariablesThread AttributesThe pthread_once FunctionKeysCancellationSchedulingSignalsThreadsafe System InterfacesError ReportingSystem Interfaces and Cancellation-SafetyProcess-Blocking CallsProcess Management
C. Pthreads Quick Reference
D. About the Authors
Index
About the Authors
Colophon
Copyright

Content preview from PThreads Programming

Chapter 5. Pthreads and UNIX

In this chapter:

Because operating systems are inherently designed to accommodate processes, not threads, system implementors must often bend tradition to introduce thread support. It’s as if we were to discover one day that the sun did not orbit the earth, but that, in reality, the earth revolves around the sun. The process is no longer central to our operating system world. Whereas it used to schedule processes, our system now schedules threads—no minor feat because, to do so, it must rototill its internal data structures and reinvent some of its most basic notions. What’s more, whereas it used to deliver signals to processes, it now must deliver signals to threads. How it selects the thread to which it delivers a given signal is yet another added complexity.

Further, the operating system has always allowed us to perform certain operations on processes that become riddles in the world of threads. If we now consider a process to be a sort of container for threads, and we recognize that all threads share their process’s address space, what happens when one of these threads launches an operation that has processwide ramifications? Does a fork result in a copy of the entire process, including all existing threads? Does an exec ...

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PThreads Programming

by Dick Buttlar, Jacqueline Farrell, Bradford Nichols

Chapter 5. Pthreads and UNIX

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