Programming with POSIX Threads

Transcription

1 Programming with POSIX Threads David R. Butenhof :vaddison-wesley Boston San Francisco New York Toronto Montreal London Munich Paris Madrid Capetown Sidney Tokyo Singapore Mexico City

2 Contents List of Example Programs Preface Intended audience About the author Acknowledgments xii xv xvi xvi xvii 1 Introduction The "bailing programmers" Definitions and terminology Asynchronous Concurrency Uniprocessor and multiprocessor Parallelism Thread safety and reentrancy Concurrency control functions Asynchronous programming is intuitive because UNIX is asynchronous because the world is asynchronous About the examples in this book Asynchronous programming, by example The baseline, synchronous version A version using multiple processes Aversion using multiple threads Summary Benefits of threading Parallelism Concurrency Programming model Costs of threading Computing overhead Programming discipline Harder to debug To thread or not to thread? POSIX thread concepts Architectural overview Types and interfaces 30 vii

3 viii Contents Checking for errors 31 2 Threads Creating and using threads The Life of a thread Creation Startup Running and blocking Termination Recycling 44 3 Synchronization Invariants, critical sections, and predicates Mutexes Creating and destroying a mutex Locking and =locking a mutex Nonblocking mutex locks Using mutexes for atomicity Sizing a mutex to fit the job Using more than one mutex Lock hierarchy Lock chaining Condition variables Creating and destroying a condition variable Waiting an a condition variable Waking condition variable waiters One final alarm program Memory visibility between threads 88 4 A few ways to use threads Pipeline Work Crew Client/Server Advanced threaded programming One-time initialization Attributes objects Mutex attributes Condition variable attributes Thread attributes Cancellation Deferred cancelability Asynchronous cancelability 150

4 Contents ix Cleaning up Thread-specific data Creating thread-specific data Using thread-specific data Using destructor functions Realtime scheduling POSIX realtime options Scheduling policies and priorities Contention scope and allocation domain Problems with realtime scheduling Priority-aware mutexes Priority ceiling mutexes Priority inheritance mutexes Threads and kernet entities Many-to-one (user level) One-to-one (kernel level) Many-to-few (two level) POSIX adjusts to threads fork Fork handlers exec Process exit Stdio flockfile and funlockfile getchar_unlocked and putchar_unlocked Thread-safe functions User and terminal identification Directory searching String token Time representation Random number generation Group and user database Signals Signal actions Signal masks pthread_kill sigwait and sigwaitinfo SIGEV THREAD Semaphores: synchronizing with a signal-catching function "Real code" 241

5 x Contents 7.1 Extended synchronization Barriers Read-write locks Work queue manager But what about existing libraries? Modifying libraries to be thread-safe Living with legacy libraries Hints to avoid debugging Avoiding incorrect code Avoid relying on "thread inertia" Never bet your mortgage on a thread race Cooperate to avoid deadlocks Beware of priority inversion Never share condition variables between predicates Sharing stacks and related memory corrupters Auoiding pesformance problems Beware of concurrent serialization Use the right number of mutexes Too many mutexes will not help Never fight over cache lines POSIX threads mini-reference POSIX c-1995 options POSIX c-1995 limits POSIX c-1995 inteifaces Error detection and reporting Use of void* type Threads Mutexes Condition variables Cancellation Thread-specific data Realtime scheduling Fork handlers Stdio Thread-safe functions Signals Semaphores Future standardization X/ Open XSH5 [UNIX98] 347

6 Contents xi POSIX options for XSH Mutex type Set concurrency level Stack guard size Parallel 1/ Cancellation points POSIX j Barriers Read-write locks Spinlocks Condition variable wait clock Thread abort POSIX Bibliography 363 Thread resources an the Internet 367 Index 369