PTHREAD_ATTR_SETSCOPE(3)				     Linux Programmer's Manual					  PTHREAD_ATTR_SETSCOPE(3)

NAME

       pthread_attr_setscope, pthread_attr_getscope - set/get contention scope attribute in thread attributes object

SYNOPSIS

       #include <pthread.h>

       int pthread_attr_setscope(pthread_attr_t *attr, int scope);
       int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);

       Compile and link with -pthread.

DESCRIPTION

       The  pthread_attr_setscope()  function sets the contention scope attribute of the thread attributes object referred to by attr to the value
       specified in scope.  The contention scope attribute defines the set of threads against which a thread competes for resources  such  as  the
       CPU.  POSIX.1 specifies two possible values for scope:

       PTHREAD_SCOPE_SYSTEM
	      The  thread  competes for resources with all other threads in all processes on the system that are in the same scheduling allocation
	      domain (a group of one or more processors).  PTHREAD_SCOPE_SYSTEM threads are scheduled relative to one another according  to  their
	      scheduling policy and priority.

       PTHREAD_SCOPE_PROCESS
	      The  thread  competes for resources with all other threads in the same process that were also created with the PTHREAD_SCOPE_PROCESS
	      contention scope.  PTHREAD_SCOPE_PROCESS threads are scheduled relative to other threads in the process according to their  schedul-
	      ing  policy and priority.  POSIX.1 leaves it unspecified how these threads contend with other threads in other process on the system
	      or with other threads in the same process that were created with the PTHREAD_SCOPE_SYSTEM contention scope.

       POSIX.1 requires that an implementation support at least one of these contention scopes.   Linux  supports  PTHREAD_SCOPE_SYSTEM,  but  not
       PTHREAD_SCOPE_PROCESS.

       On systems that support multiple contention scopes, then, in order for the parameter setting made by pthread_attr_setscope() to have effect
       when calling pthread_create(3), the caller  must  use  pthread_attr_setinheritsched(3)  to  set	the  inherit-scheduler	attribute  of  the
       attributes object attr to PTHREAD_EXPLICIT_SCHED.

       The pthread_attr_getscope() function returns the contention scope attribute of the thread attributes object referred to by attr in the buf-
       fer pointed to by scope.

RETURN VALUE

       On success, these functions return 0; on error, they return a nonzero error number.

ERRORS

       pthread_attr_setscope() can fail with the following errors:

       EINVAL An invalid value was specified in scope.

       ENOTSUP
	      scope specified the value PTHREAD_SCOPE_PROCESS, which is not supported on Linux.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       +-------------------------+---------------+---------+
       |Interface		 | Attribute	 | Value   |
       +-------------------------+---------------+---------+
       |pthread_attr_setscope(), | Thread safety | MT-Safe |
       |pthread_attr_getscope()  |		 |	   |
       +-------------------------+---------------+---------+
CONFORMING TO

       POSIX.1-2001, POSIX.1-2008.

NOTES

       The  PTHREAD_SCOPE_SYSTEM  contention  scope  typically	indicates that a user-space thread is bound directly to a single kernel-scheduling
       entity.	This is the case on Linux for the obsolete LinuxThreads implementation and the modern NPTL  implementation,  which  are  both  1:1
       threading implementations.

       POSIX.1 specifies that the default contention scope is implementation-defined.

SEE ALSO

       pthread_attr_init(3), pthread_attr_setaffinity_np(3), pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3),
       pthread_attr_setschedpolicy(3), pthread_create(3), pthreads(7)

COLOPHON

       This page is part of release 4.15 of the Linux man-pages project.  A description of the project, information about reporting bugs, and the
       latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

Linux								    2017-09-15						  PTHREAD_ATTR_SETSCOPE(3)