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pthread_attr_setscope(3) — Linux manual page

pthread_attr_setscope(3) Library Functions Manualpthread_attr_setscope(3)

NAME        top

       pthread_attr_setscope, pthread_attr_getscope - set/get contention       scope attribute in thread attributes object

LIBRARY        top

       POSIX threads library (libpthread,-lpthread)

SYNOPSIS        top

#include <pthread.h>int pthread_attr_setscope(pthread_attr_t *attr, intscope);int pthread_attr_getscope(const pthread_attr_t *restrictattr,int *restrictscope);

DESCRIPTION        top

       Thepthread_attr_setscope() function sets the contention scope       attribute of the thread attributes object referred to byattr to       the value specified inscope.  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       forscope: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_SYSTEMthreads 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 thePTHREAD_SCOPE_PROCESScontention scope.PTHREAD_SCOPE_PROCESSthreads 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 thePTHREAD_SCOPE_SYSTEMcontention              scope.       POSIX.1 requires that an implementation support at least one of       these contention scopes.  Linux supportsPTHREAD_SCOPE_SYSTEM, but       notPTHREAD_SCOPE_PROCESS.       On systems that support multiple contention scopes, then, in order       for the parameter setting made bypthread_attr_setscope() to have       effect when callingpthread_create(3), the caller must usepthread_attr_setinheritsched(3) to set the inherit-scheduler       attribute of the attributes objectattr toPTHREAD_EXPLICIT_SCHED.       Thepthread_attr_getscope() function returns the contention scope       attribute of the thread attributes object referred to byattr in       the buffer pointed to byscope.

RETURN VALUE        top

       On success, these functions return 0; on error, they return a       nonzero error number.

ERRORS        top

pthread_attr_setscope() can fail with the following errors:EINVALAn invalid value was specified inscope.ENOTSUPscope specified the valuePTHREAD_SCOPE_PROCESS, which is              not supported on Linux.

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │pthread_attr_setscope(),             │ Thread safety │ MT-Safe │       │pthread_attr_getscope()              │               │         │       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS        top

       POSIX.1-2008.

HISTORY        top

       POSIX.1-2001.

NOTES        top

       ThePTHREAD_SCOPE_SYSTEMcontention 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        top

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        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17pthread_attr_setscope(3)

Pages that refer to this page:pthread_attr_init(3), pthread_attr_setinheritsched(3), pthread_getattr_default_np(3), pthread_getattr_np(3), pthread_setconcurrency(3)

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