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:

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 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:

ATTRIBUTES

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

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)