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(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.1-2001 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.1-2001 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.1-2001 only requires that an implementation support one of these contention scopes, but permits both to be supported.  Linux supports
       PTHREAD_SCOPE_SYSTEM, but not PTHREAD_SCOPE_PROCESS.

       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.

CONFORMING TO

       POSIX.1-2001.

NOTES

       The PTHREAD_SCOPE_SYSTEM contention scope typically indicates that a userspace 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.1-2001 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 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2008-10-24						  PTHREAD_ATTR_SETSCOPE(3)