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 alloca-
	      tion   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  scheduling  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_set-
       inheritsched(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
       buffer 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 imple-
       mentation  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 4.10 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				  2015-08-08	      PTHREAD_ATTR_SETSCOPE(3)