#include <pthread.h>int pthread_attr_setscope(pthread_attr_t *attr, int scope);int pthread_attr_getscope(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.1-2001 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.1-2001 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.1-2001 only requires that an implementation support one of these
contention scopes, but permits both to be supported.
Linux supports
PTHREAD_SCOPE_SYSTEM,
but not
PTHREAD_SCOPE_PROCESS.
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 non-zero 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.
CONFORMING TO
POSIX.1-2001.
NOTES
The
PTHREAD_SCOPE_SYSTEM
contention scope typically indicates that a userspace thread is
bound directly to a single kernel-scheduling entity.
This is the case on Linux for the obsolete LinuxThread implementation
and the modern NPTL implementation,
which are both 1:1 threading implementations.
POSIX.1-2001 specifies that the default contention scope is
implementation-defined.
This page is part of release 3.14 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
