mirror of https://github.com/mkerrisk/man-pages
92 lines
2.8 KiB
Groff
92 lines
2.8 KiB
Groff
.\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
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.\"
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.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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.\" This is free documentation; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License as
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.\" published by the Free Software Foundation; either version 2 of
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.\" the License, or (at your option) any later version.
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.\"
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.\" The GNU General Public License's references to "object code"
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.\" and "executables" are to be interpreted as the output of any
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.\" document formatting or typesetting system, including
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.\" intermediate and printed output.
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.\"
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.\" This manual is distributed in the hope that it will be useful,
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.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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.\" GNU General Public License for more details.
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.\"
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.\" You should have received a copy of the GNU General Public
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.\" License along with this manual; if not, see
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.\" <http://www.gnu.org/licenses/>.
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.\" %%%LICENSE_END
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.\"
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.\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
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.\" First version written
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.\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
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.\" revision
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.\"
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.TH SCHED_YIELD 2 2017-09-15 "Linux" "Linux Programmer's Manual"
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.SH NAME
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sched_yield \- yield the processor
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.SH SYNOPSIS
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.B #include <sched.h>
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.PP
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.B int sched_yield(void);
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.SH DESCRIPTION
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.BR sched_yield ()
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causes the calling thread to relinquish the CPU.
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The thread is moved to the end of the queue for its static
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priority and a new thread gets to run.
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.SH RETURN VALUE
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On success,
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.BR sched_yield ()
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returns 0.
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On error, \-1 is returned, and
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.I errno
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is set appropriately.
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.SH ERRORS
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In the Linux implementation,
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.BR sched_yield ()
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always succeeds.
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.SH CONFORMING TO
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POSIX.1-2001, POSIX.1-2008.
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.SH NOTES
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If the calling thread is the only thread in the highest
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priority list at that time,
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it will continue to run after a call to
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.BR sched_yield ().
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.PP
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POSIX systems on which
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.BR sched_yield ()
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is available define
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.B _POSIX_PRIORITY_SCHEDULING
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in
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.IR <unistd.h> .
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.PP
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Strategic calls to
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.BR sched_yield ()
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can improve performance by giving other threads or processes
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a chance to run when (heavily) contended resources (e.g., mutexes)
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have been released by the caller.
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Avoid calling
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.BR sched_yield ()
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unnecessarily or inappropriately
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(e.g., when resources needed by other
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schedulable threads are still held by the caller),
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since doing so will result in unnecessary context switches,
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which will degrade system performance.
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.PP
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.BR sched_yield ()
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is intended for use with real-time scheduling policies (i.e.,
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.BR SCHED_FIFO
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or
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.BR SCHED_RR ).
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Use of
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.BR sched_yield ()
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with nondeterministic scheduling policies such as
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.BR SCHED_OTHER
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is unspecified and very likely means your application design is broken.
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.SH SEE ALSO
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.BR sched (7)
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