.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
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-.TH PTHREAD_ATTR_SETSCOPE 3 2008-10-24 "Linux" "Linux Programmer's Manual"
+.TH PTHREAD_ATTR_SETSCOPE 3 2021-03-22 "Linux man-pages (unreleased)" "Linux Programmer's Manual"
.SH NAME
pthread_attr_setscope, pthread_attr_getscope \- set/get contention scope
attribute in thread attributes object
+.SH LIBRARY
+POSIX threads library
+.RI ( libpthread ", " \-lpthread )
.SH SYNOPSIS
.nf
.B #include <pthread.h>
-
-.BI "int pthread_attr_setscope(pthread_attr_t *" attr \
-", int " scope );
-.BI "int pthread_attr_getscope(pthread_attr_t *" attr \
-", int *" scope );
-.sp
-Compile and link with \fI\-pthread\fP.
+.PP
+.BI "int pthread_attr_setscope(pthread_attr_t *" attr ", int " scope );
+.BI "int pthread_attr_getscope(const pthread_attr_t *restrict " attr ,
+.BI " int *restrict " scope );
+.fi
.SH DESCRIPTION
The
.BR pthread_attr_setscope ()
.IR 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
+POSIX.1 specifies two possible values for
.IR scope :
.TP
.B PTHREAD_SCOPE_SYSTEM
.B PTHREAD_SCOPE_PROCESS
The thread competes for resources with all other threads
in the same process that were also created with the
-.BR PTHREAD_SCOPE_PROCESS
+.B PTHREAD_SCOPE_PROCESS
contention scope.
-.BR PTHREAD_SCOPE_PROCESS
+.B 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
+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
.B PTHREAD_SCOPE_SYSTEM
contention scope.
.PP
-POSIX.1-2001 only requires that an implementation support one of these
-contention scopes, but permits both to be supported.
+POSIX.1 requires that an implementation support at least one of these
+contention scopes.
Linux supports
.BR PTHREAD_SCOPE_SYSTEM ,
but not
.BR PTHREAD_SCOPE_PROCESS .
-
+.PP
+On systems that support multiple contention scopes, then,
+in order for the parameter setting made by
+.BR pthread_attr_setscope ()
+to have effect when calling
+.BR pthread_create (3),
+the caller must use
+.BR pthread_attr_setinheritsched (3)
+to set the inherit-scheduler attribute of the attributes object
+.I attr
+to
+.BR PTHREAD_EXPLICIT_SCHED .
+.PP
The
.BR pthread_attr_getscope ()
function returns the contention scope attribute of the
.IR scope .
.SH RETURN VALUE
On success, these functions return 0;
-on error, they return a non-zero error number.
+on error, they return a nonzero error number.
.SH ERRORS
.BR pthread_attr_setscope ()
can fail with the following errors:
.IR scope .
.TP
.B ENOTSUP
-.IR scope
+.I scope
specified the value
.BR PTHREAD_SCOPE_PROCESS ,
which is not supported on Linux.
-.SH CONFORMING TO
-POSIX.1-2001.
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.ad l
+.nh
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface Attribute Value
+T{
+.BR pthread_attr_setscope (),
+.BR pthread_attr_getscope ()
+T} Thread safety MT-Safe
+.TE
+.hy
+.ad
+.sp 1
+.SH STANDARDS
+POSIX.1-2001, POSIX.1-2008.
.SH NOTES
The
.B PTHREAD_SCOPE_SYSTEM
-contention scope typically indicates that a userspace thread is
+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 LinuxThread implementation
+This is the case on Linux for the obsolete LinuxThreads implementation
and the modern NPTL implementation,
which are both 1:1 threading implementations.
-
-POSIX.1-2001 specifies that the default contention scope is
+.PP
+POSIX.1 specifies that the default contention scope is
implementation-defined.
.SH SEE ALSO
+.ad l
+.nh
.BR pthread_attr_init (3),
.BR pthread_attr_setaffinity_np (3),
.BR pthread_attr_setinheritsched (3),
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