pthread_attr_setscope, pthread_attr_getscope - set/get contention scope
attribute in thread attributes object
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.
() 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
- 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
(3), the caller must use
(3) to set the inherit-scheduler attribute
of the attributes object attr
() function returns the contention scope
attribute of the thread attributes object referred to by attr
buffer pointed to by scope
On success, these functions return 0; on error, they return a nonzero error
() can fail with the following errors:
- An invalid value was specified in scope.
- scope specified the value PTHREAD_SCOPE_PROCESS, which is
not supported on Linux.
For an explanation of the terms used in this section, see attributes
|pthread_attr_setscope (), pthread_attr_getscope ()
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.