POSIX Threads, usually referred to as Pthreads, is a POSIX
POSIX
POSIX , an acronym for "Portable Operating System Interface", is a family of standards specified by the IEEE for maintaining compatibility between operating systems...
In computer science, a thread of execution is the smallest unit of processing that can be scheduled by an operating system. The implementation of threads and processes differs from one operating system to another, but in most cases, a thread is contained inside a process...
s. The standard, POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995), defines an API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
for creating and manipulating threads.
Implementations of the API are available on many Unix-like
Unix-like
A Unix-like operating system is one that behaves in a manner similar to a Unix system, while not necessarily conforming to or being certified to any version of the Single UNIX Specification....
POSIX-conformant operating systems such as FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
NetBSD is a freely available open source version of the Berkeley Software Distribution Unix operating system. It was the second open source BSD descendant to be formally released, after 386BSD, and continues to be actively developed. The NetBSD project is primarily focused on high quality design,...
OpenBSD is a Unix-like computer operating system descended from Berkeley Software Distribution , a Unix derivative developed at the University of California, Berkeley. It was forked from NetBSD by project leader Theo de Raadt in late 1995...
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
DR-DOS is an MS-DOS-compatible operating system for IBM PC-compatible personal computers, originally developed by Gary Kildall's Digital Research and derived from Concurrent PC DOS 6.0, which was an advanced successor of CP/M-86...
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
implementations also exist: within the SFU/SUA subsystem which provides a native implementation of a number of POSIX APIs, and also within third-party packages such as pthreads-w32, which implements pthreads on top of existing Windows API
Windows API
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces available in the Microsoft Windows operating systems. It was formerly called the Win32 API; however, the name "Windows API" more accurately reflects its roots in 16-bit Windows and its support on...
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
In computer programming, a data type is a classification identifying one of various types of data, such as floating-point, integer, or Boolean, that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of...
, functions and constants. It is implemented with a pthread.h header and a thread library.
There are around 100 Pthreads procedures, all prefixed "pthread_" and they can be categorized into four groups:
Thread management - creating, joining threads etc.
In computer science, synchronization refers to one of two distinct but related concepts: synchronization of processes, and synchronization of data. Process synchronization refers to the idea that multiple processes are to join up or handshake at a certain point, so as to reach an agreement or...
between threads using read/write locks and barriers
In computer science, a semaphore is a variable or abstract data type that provides a simple but useful abstraction for controlling access by multiple processes to a common resource in a parallel programming environment....
API works with POSIX threads but is not part of threads standard, having been defined in the POSIX.1b, Real-time extensions (IEEE Std 1003.1b-1993) standard. Consequently the semaphore procedures are prefixed by "sem_" instead of "pthread_".
The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...
compiler requires the use of the command line operator "-pthread" to compile, such that a line to compile might read: "gcc -pthread pthread_program.c".
int main(void)
{
pthread_t threads[NUM_THREADS];
int thread_args[NUM_THREADS];
int rc, i;
/* create all threads */
for (i=0; i
thread_args[i] = i;
printf("In main: creating thread %d\n", i);
rc = pthread_create(&threads[i], NULL, TaskCode, (void *) &thread_args[i]);
assert(0
rc);
}
/* wait for all threads to complete */
for (i=0; i
rc = pthread_join(threads[i], NULL);
assert(0
rc);
}
exit(EXIT_SUCCESS);
}
This program creates five threads, each executing the function TaskCode that prints the unique number of this thread to standard output. If a programmer wanted the threads to communicate with each other, this would require defining a variable outside of the scope of any of the functions, making it a global variable
Global variable
In computer programming, a global variable is a variable that is accessible in every scope . Interaction mechanisms with global variables are called global environment mechanisms...
.
POSIX Threads for Windows
Windows does not support the pthreads standard natively, therefore the Pthreads-w32 project seeks to provide a portable and open-source implementation. It can be also used to port Unix
Unix
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
software (which use pthreads) with little or no modification to the Windows platform. With some additional patches the last version 2.8.0 is compatible with 64-bit Windows systems.
Interix is the name of an optional, full-featured POSIX and Unix environment subsystem for Microsoft's Windows NT-based operating systems.Interix is a component of the Services for Unix release 3.0 and 3.5...
environment subsystem available in the Windows Services for UNIX/Subsystem for UNIX-based Applications package provides a native port of the pthreads API, i.e. not mapped on Win32/Win64 API but built directly on the operating system syscall interface.
OpenMP is an API that supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran, on most processor architectures and operating systems, including Linux, Unix, AIX, Solaris, Mac OS X, and Microsoft Windows platforms...
The Native POSIX Thread Library is a software feature that enables the Linux kernel to run programs written to use POSIX Threads efficiently.-History:...
DCEThreads is an implementation of POSIX Draft 4 threads.-History:DCE/RPC was under development, but the POSIX committee had not finalised POSIX threads at the time...
clone is a system call on the Linux kernel related to multithreading. In practice, one should try to avoid calling clone directly, but instead use a threading library which use clone when starting a thread .The syntax for calling clone under a Linux program is: #include int clone clone is a...
In the POSIX thread API, the function pthread_cond_wait is used to wait on a condition variable. A naive programmer might expect that when a thread returns from this function, the condition associated with the condition variable will be true...
Thread-local storage is a computer programming method that uses static or global memory local to a thread.This is sometimes needed because normally all threads in a process share the same address space, which is sometimes undesirable...
GNU Pth is a POSIX/ANSI-C based user-space thread library for UNIX platforms which provides priority-based scheduling for multithreading applications...
FSU Pthreads is an implementation of POSIX Threads, a standard for threads, written for Ada. It was developed by Ted Baker and his computer science students at Florida State University for use in the Ada programming language...
The beginthread function creates a new thread of execution within the current process. It is part of the Microsoft Windows runtime library and is declared in the process.h header file.-Prototype:-Func:Thread execution starts at the beginning of the function func...
(a subroutine within Windows for creating a new thread and unix thread)
