From Wikipedia, the free encyclopedia

POSIX Threads is a POSIX standard for threads. The standard defines an API for creating and manipulating threads.

Libraries implementing the POSIX Threads standard are often named Pthreads. Pthreads are most commonly used on Unix-like POSIX systems such as Linux and Solaris, but Microsoft Windows implementations also exist. For example, the pthreads-w32 is available and supports a subset of the Pthread API [1]. (Note: in text, Pthreads is written with an upper-case P.^{[citation needed]})

Pthreads defines a set of C programming language types and procedure calls. It is implemented with a pthread.h header and a thread library.

Data types

• pthread_t: handle to a thread
• pthread_attr_t: thread attributes

Thread manipulation functions (arguments omitted for brevity):

• pthread_create(): create a thread
• pthread_exit(): terminate current thread
• pthread_cancel(): cancel execution of another thread
• pthread_join(): block current thread until another one terminates
• pthread_attr_init(): initialize thread attributes
• pthread_attr_setdetachstate(): set the detachstate attribute (whether thread can be joined on termination)
• pthread_attr_getdetachstate(): get the detachstate attribute
• pthread_attr_destroy(): destroy thread attributes
• pthread_kill(): send a signal to a thread

Synchronization functions: for mutexes and condition variables

• pthread_mutex_init()
• pthread_mutex_destroy()
• pthread_mutex_lock(): acquire mutex lock (blocking)
• pthread_mutex_trylock(): acquire mutex lock (non-blocking)
• pthread_mutex_unlock(): release mutex lock
• pthread_cond_init()
• pthread_cond_destroy()
• pthread_cond_signal(): signal a condition
• pthread_cond_wait(): wait on a condition

An example of using Pthreads in C:

#include 
#include 
#include 
#include 
 
void *thread_func( void *vptr_args );
 
void do_some_work( void ){
  time_t start_time = time(NULL);
 
  while (time(NULL) == start_time);  /* busy-wait for 0-1 seconds */
}
 
int main( void ){
  int i, j;
  pthread_t thread;
 
  pthread_create( &thread, NULL, &thread_func, NULL );
 
  for( j= 0; j < 20; ++j ){
    fprintf( stdout, "a\n" );
 
    do_some_work();
  }
 
  pthread_join( thread, NULL );
 
  exit( EXIT_SUCCESS );
}
 
void *thread_func( void *vptr_args ){
  int i, j;
 
  for( j= 0; j < 20; ++j ){
    fprintf( stderr, "  b\n" );
 
    do_some_work();
  }
  return NULL;
}

This program creates a new thread that prints lines containing 'b', while the main thread prints lines containing 'a'. The output is interleaved between 'a' and 'b' as a result of execution switching between the two threads. More tutorials can be found below in the links section.

• David R. Butenhof: Programming with POSIX Threads, Addison-Wesley, ISBN 0-201-63392-2
• Bradford Nichols, Dick Buttlar, Jacqueline Proulx Farell: Pthreads Programming, O'Reilly & Associates, ISBN 1-56592-115-1
• Charles J. Northrup: Programming with UNIX Threads, John Wiley & Sons, ISBN 0-471-13751-0

• Native POSIX Thread Library (NPTL)
• Spurious wakeup
• GNU Portable Threads
• FSU Pthreads

• POSIX Threading and Synchronous Wrappers
• Multithreaded Programming (Pthreads Tutorial)
• Pthreads Tutorial
• C/C++ Tutorial: using Pthreads
• Article "POSIX threads explained" by Daniel Robbins (Gentoo Linux founder)
• Interview "Ten Questions with David Butenhof about Parallel Programming and POSIX Threads" by Michael Suess
• Open Source POSIX Threads for Win32
• The Open Group Base Specifications Issue 6, IEEE Std 1003.1
• GNU Portable threads

v • d • e Parallel computing topics
General	High-performance computing
Parallelism	Bit-level parallelism · Instruction level parallelism · Data parallelism · Task parallelism
Theory	Speedup · Amdahl's law · Flynn's taxonomy (SISD • SIMD • MISD • MIMD) · Cost efficiency · Gustafson's law · Karp-Flatt metric
Elements	Process · Thread · Fiber · Parallel Random Access Machine
Coordination	Multiprocessing · Multithreading · Multitasking · Memory coherency · Cache coherency · Barrier · Synchronization · Distributed computing · Grid computing
Programming	Programming model · Implicit parallelism · Explicit parallelism
Hardware	Computer cluster · Beowulf · Symmetric multiprocessing · Non-Uniform Memory Access · Cache only memory architecture · Asymmetric multiprocessing · Simultaneous multithreading · Shared memory · Distributed memory · Massively parallel processing · Superscalar processing · Vector processing · Supercomputer · Stream processing · GPGPU
Software	Distributed shared memory  · Application checkpointing · Warewulf
APIs	POSIX Threads · OpenMP · Message Passing Interface (MPI)
Problems	Embarrassingly parallel · Grand Challenge · Software lockout