pthread_attr_setscope(3) Library Functions Manual pthread_attr_setscope(3)
NAME
pthread_attr_setscope, pthread_attr_getscope - set/get contention scope
attribute in thread attributes object
LIBRARY
POSIX threads library (libpthread, -lpthread)
SYNOPSIS
#include <pthread.h>
int pthread_attr_setscope(pthread_attr_t *attr, int scope);
int pthread_attr_getscope(const pthread_attr_t *restrict attr,
int *restrict scope);
DESCRIPTION
The pthread_attr_setscope() function sets the contention scope at-
tribute 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 an-
other 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 attrib-
utes object attr to PTHREAD_EXPLICIT_SCHED.
The pthread_attr_getscope() function returns the contention scope at-
tribute 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 attrib-
utes(7).
┌───────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────────────────┼───────────────┼─────────┤
│ pthread_attr_setscope(), │ Thread safety │ MT-Safe │
│ pthread_attr_getscope() │ │ │
└───────────────────────────────────────────┴───────────────┴─────────┘
STANDARDS
POSIX.1-2008.
HISTORY
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 en-
tity. 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)
Linux man-pages 6.7 2023-10-31 pthread_attr_setscope(3)
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