In the Linux

Linux

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...

 operating system, LinuxThreads was a partial implementation of POSIX Threads

POSIX Threads

POSIX Threads, usually referred to as Pthreads, is a POSIX standard for threads. The standard, POSIX.1c, Threads extensions , defines an API for creating and manipulating threads....

 that has since been superseded by the Native POSIX Thread Library

Native POSIX Thread Library

The Native POSIX Thread Library is a software feature that enables the Linux kernel to run programs written to use POSIX Threads efficiently.-History:...

 (NPTL).

LinuxThreads had a number of problems, mainly owing to the implementation, which used the clone

Clone (Linux system call)

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...

 system call to create a new process

Process (computing)

In computing, a process is an instance of a computer program that is being executed. It contains the program code and its current activity. Depending on the operating system , a process may be made up of multiple threads of execution that execute instructions concurrently.A computer program is a...

 sharing the parent's address space

Address space

In computing, an address space defines a range of discrete addresses, each of which may correspond to a network host, peripheral device, disk sector, a memory cell or other logical or physical entity.- Overview :...

. For example, threads had distinct process identifier

Process identifier

In computing, the process identifier is a number used by most operating system kernels to uniquely identify a process...

s, causing problems for signal

Signal (computing)

A signal is a limited form of inter-process communication used in Unix, Unix-like, and other POSIX-compliant operating systems. Essentially it is an asynchronous notification sent to a process in order to notify it of an event that occurred. When a signal is sent to a process, the operating system...

 handling; LinuxThreads used the signals SIGUSR1

SIGUSR1

On POSIX-compliant platforms, SIGUSR1 and SIGUSR2 are signals sent to a process to indicate user-defined conditions. The symbolic constants for them are defined in the header file signal.h. Symbolic signal names are used because signal numbers can vary across platforms.-Etymology:SIG is a common...

 and SIGUSR2 for inter-thread coordination, meaning these signals could not be used by programs.

To improve the situation, two competing projects were started to develop a replacement; NGPT (Next Generation POSIX Threads) and NPTL. NPTL won out and is today shipped with the vast majority of Linux systems. , LinuxThreads may still be seen on production systems, particularly those using version 2.4 or lower of the Linux kernel

Linux kernel

The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....

, as NPTL requires facilities which were specifically added into the 2.6 version of the kernel for its use.

External links

• The LinuxThreads library, Xavier Leroy Home Page