NAME         top

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

SYNOPSIS         top

       #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         top

       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:

              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.

              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

       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         top

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

ERRORS         top

       pthread_attr_setscope() can fail with the following errors:

       EINVAL An invalid value was specified in scope.

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

ATTRIBUTES         top

       For an explanation of the terms used in this section, see

       │Interface                Attribute     Value   │
       │pthread_attr_setscope(), │ Thread safety │ MT-Safe │
       │pthread_attr_getscope()  │               │         │

CONFORMING TO         top

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

NOTES         top

       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

SEE ALSO         top

       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         top

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       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at

Linux                            2015-08-08         PTHREAD_ATTR_SETSCOPE(3)