man2/sched_yield.2

   1 .\" Copyright (C) Tom Bjorkholm & Markus Kuhn, 1996
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  22 .\" 1996-04-01 Tom Bjorkholm <tomb@mydata.se>
  23 .\"            First version written
  24 .\" 1996-04-10 Markus Kuhn <mskuhn@cip.informatik.uni-erlangen.de>
  25 .\"            revision
  26 .\"
  27 .TH SCHED_YIELD 2 2008-10-18 "Linux" "Linux Programmer's Manual"
  28 .SH NAME
  29 sched_yield \- yield the processor
  30 .SH SYNOPSIS
  31 .B #include <sched.h>
  32 .sp
  33 .B int sched_yield(void);
  34 .SH DESCRIPTION
  35 .BR sched_yield ()
  36 causes the calling thread to relinquish the CPU.
  37 The thread is moved to the end of the queue for its static
  38 priority and a new thread gets to run.
  39 .SH RETURN VALUE
  40 On success,
  41 .BR sched_yield ()
  42 returns 0.
  43 On error, \-1 is returned, and
  44 .I errno
  45 is set appropriately.
  46 .SH ERRORS
  47 In the Linux implementation,
  48 .BR sched_yield ()
  49 always succeeds.
  50 .SH CONFORMING TO
  51 POSIX.1-2001.
  52 .SH NOTES
  53 If the calling thread is the only thread in the highest
  54 priority list at that time,
  55 it will continue to run after a call to
  56 .BR sched_yield ().
  57
  58 POSIX systems on which
  59 .BR sched_yield ()
  60 is available define
  61 .B _POSIX_PRIORITY_SCHEDULING
  62 in \fI<unistd.h>\fP.
  63
  64 Strategic calls to
  65 .BR sched_yield ()
  66 can improve performance by giving other threads or processes
  67 a chance to run when (heavily) contended resources (e.g., mutexes)
  68 have been released by the caller.
  69 Avoid calling
  70 .BR sched_yield ()
  71 unnecessarily or inappropriately
  72 (e.g., when resources needed by other
  73 schedulable threads are still held by the caller),
  74 since doing so will result in unnecessary context switches,
  75 which will degrade system performance.
  76 .SH SEE ALSO
  77 .BR sched_setscheduler (2)
  78 for a description of Linux scheduling
  79 .PP
  80 .I Programming for the real world \- POSIX.4
  81 by Bill O. Gallmeister, O'Reilly & Associates, Inc., ISBN 1-56592-074-0.