mirror of https://github.com/mkerrisk/man-pages
125 lines
4.1 KiB
Groff
125 lines
4.1 KiB
Groff
.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
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.\" <mtk.manpages@gmail.com>
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\"
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.TH PTHREAD_ATTR_SETSCOPE 3 2008-10-24 "Linux" "Linux Programmer's Manual"
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.SH NAME
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pthread_attr_setscope, pthread_attr_getscope \- set/get contention scope
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attribute in thread attributes object
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.SH SYNOPSIS
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.nf
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.B #include <pthread.h>
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.BI "int pthread_attr_setscope(pthread_attr_t *" attr \
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", int " scope );
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.BI "int pthread_attr_getscope(pthread_attr_t *" attr \
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", int *" scope );
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.sp
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Compile and link with \fI\-pthread\fP.
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.SH DESCRIPTION
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The
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.BR pthread_attr_setscope ()
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function sets the contention scope attribute of the
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thread attributes object referred to by
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.I attr
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to the value specified in
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.IR scope .
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The contention scope attribute defines the set of threads
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against which a thread competes for resources such as the CPU.
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POSIX.1-2001 specifies two possible values for
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.IR scope :
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.TP
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.B PTHREAD_SCOPE_SYSTEM
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The thread competes for resources with all other threads
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in all processes on the system that are in the same scheduling
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allocation domain (a group of one or more processors).
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.B PTHREAD_SCOPE_SYSTEM
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threads are scheduled relative to one another
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according to their scheduling policy and priority.
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.TP
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.B PTHREAD_SCOPE_PROCESS
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The thread competes for resources with all other threads
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in the same process that were also created with the
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.BR PTHREAD_SCOPE_PROCESS
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contention scope.
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.BR PTHREAD_SCOPE_PROCESS
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threads are scheduled relative to other threads in the process
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according to their scheduling policy and priority.
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POSIX.1-2001 leaves it unspecified how these threads contend
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with other threads in other process on the system or
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with other threads in the same process that
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were created with the
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.B PTHREAD_SCOPE_SYSTEM
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contention scope.
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.PP
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POSIX.1-2001 only requires that an implementation support one of these
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contention scopes, but permits both to be supported.
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Linux supports
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.BR PTHREAD_SCOPE_SYSTEM ,
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but not
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.BR PTHREAD_SCOPE_PROCESS .
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The
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.BR pthread_attr_getscope ()
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function returns the contention scope attribute of the
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thread attributes object referred to by
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.I attr
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in the buffer pointed to by
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.IR scope .
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.SH RETURN VALUE
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On success, these functions return 0;
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on error, they return a non-zero error number.
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.SH ERRORS
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.BR pthread_attr_setscope ()
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can fail with the following errors:
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.TP
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.B EINVAL
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An invalid value was specified in
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.IR scope .
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.TP
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.B ENOTSUP
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.IR scope
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specified the value
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.BR PTHREAD_SCOPE_PROCESS ,
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which is not supported on Linux.
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.SH CONFORMING TO
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POSIX.1-2001.
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.SH NOTES
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The
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.B PTHREAD_SCOPE_SYSTEM
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contention scope typically indicates that a userspace thread is
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bound directly to a single kernel-scheduling entity.
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This is the case on Linux for the obsolete LinuxThread implementation
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and the modern NPTL implementation,
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which are both 1:1 threading implementations.
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POSIX.1-2001 specifies that the default contention scope is
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implementation-defined.
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.SH SEE ALSO
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.BR pthread_attr_init (3),
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.BR pthread_attr_setaffinity_np (3),
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.BR pthread_attr_setinheritsched (3),
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.BR pthread_attr_setschedparam (3),
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.BR pthread_attr_setschedpolicy (3),
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.BR pthread_create (3),
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.BR pthreads (7)
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