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  scheduling  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  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 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.

CONFORMING TO

       POSIX.1-2001.

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.1-2001 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 3.54 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/.