PTHREAD_ATTR_SETSCOPE
Section: Linux Programmer's Manual (3)
Updated: 2017-09-15
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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(const 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 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 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_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.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
| Interface | Attribute | Value
|
|
pthread_attr_setscope(),
pthread_attr_getscope()
| Thread safety | MT-Safe
|
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)
COLOPHON
This page is part of release 4.13 of the Linux
man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
https://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- ATTRIBUTES
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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- Running on 
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