man-pages/man3p/pthread_getschedparam.3p

.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PTHREAD_GETSCHEDPARAM" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_getschedparam 
.SH NAME
pthread_getschedparam, pthread_setschedparam \- dynamic thread scheduling
parameters access (\fBREALTIME
THREADS\fP)
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
.sp
int pthread_getschedparam(pthread_t\fP \fIthread\fP\fB, int *restrict\fP
\fIpolicy\fP\fB,
.br
\ \ \ \ \ \  struct sched_param *restrict\fP \fIparam\fP\fB);
.br
int pthread_setschedparam(pthread_t\fP \fIthread\fP\fB, int\fP \fIpolicy\fP\fB,
.br
\ \ \ \ \ \  const struct sched_param *\fP\fIparam\fP\fB); \fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_getschedparam\fP() and \fIpthread_setschedparam\fP()
functions shall, respectively, get and set the scheduling
policy and parameters of individual threads within a multi-threaded
process to be retrieved and set. For SCHED_FIFO and SCHED_RR,
the only required member of the \fBsched_param\fP structure is the
priority \fIsched_priority\fP. For SCHED_OTHER, the affected
scheduling parameters are implementation-defined.
.LP
The \fIpthread_getschedparam\fP() function shall retrieve the scheduling
policy and scheduling parameters for the thread whose
thread ID is given by \fIthread\fP and shall store those values in
\fIpolicy\fP and \fIparam\fP, respectively. The priority
value returned from \fIpthread_getschedparam\fP() shall be the value
specified by the most recent \fIpthread_setschedparam\fP(),
\fIpthread_setschedprio\fP(), or \fIpthread_create\fP() call affecting
the target thread. It shall not reflect any temporary
adjustments to its priority as a result of any priority inheritance
or ceiling functions. The \fIpthread_setschedparam\fP()
function shall set the scheduling policy and associated scheduling
parameters for the thread whose thread ID is given by
\fIthread\fP to the policy and associated parameters provided in \fIpolicy\fP
and \fIparam\fP, respectively.
.LP
The \fIpolicy\fP parameter may have the value SCHED_OTHER, SCHED_FIFO,
or SCHED_RR. The scheduling parameters for the
SCHED_OTHER policy are implementation-defined. The SCHED_FIFO and
SCHED_RR policies shall have a single scheduling parameter,
\fIpriority\fP.
.LP
If _POSIX_THREAD_SPORADIC_SERVER is defined, then the \fIpolicy\fP
argument may have the value SCHED_SPORADIC, with the exception
for the \fIpthread_setschedparam\fP() function that if the scheduling
policy was not SCHED_SPORADIC at the time of the call, it is
implementation-defined whether the function is supported; in other
words, the implementation need not allow the application to
dynamically change the scheduling policy to SCHED_SPORADIC. The sporadic
server scheduling policy has the associated parameters
\fIsched_ss_low_priority\fP, \fIsched_ss_repl_period\fP, \fIsched_ss_init_budget\fP,
\fIsched_priority\fP, and
\fIsched_ss_max_repl\fP. The specified \fIsched_ss_repl_period\fP
shall be greater than or equal to the specified
\fIsched_ss_init_budget\fP for the function to succeed; if it is not,
then the function shall fail. The value of
\fIsched_ss_max_repl\fP shall be within the inclusive range [1, {SS_REPL_MAX}]
for the function to succeed; if not, the function
shall fail. 
.LP
If the \fIpthread_setschedparam\fP() function fails, the scheduling
parameters shall not be changed for the target thread.
.SH RETURN VALUE
.LP
If successful, the \fIpthread_getschedparam\fP() and \fIpthread_setschedparam\fP()
functions shall return zero; otherwise, an
error number shall be returned to indicate the error.
.SH ERRORS
.LP
The \fIpthread_getschedparam\fP() function may fail if:
.TP 7
.B ESRCH
The value specified by \fIthread\fP does not refer to an existing
thread.
.sp
.LP
The \fIpthread_setschedparam\fP() function may fail if:
.TP 7
.B EINVAL
The value specified by \fIpolicy\fP or one of the scheduling parameters
associated with the scheduling policy \fIpolicy\fP is
invalid.
.TP 7
.B ENOTSUP
An attempt was made to set the policy or scheduling parameters to
an unsupported value.
.TP 7
.B ENOTSUP
An attempt was made to dynamically change the scheduling policy to
SCHED_SPORADIC, and the implementation does not support this
change. 
.TP 7
.B EPERM
The caller does not have the appropriate permission to set either
the scheduling parameters or the scheduling policy of the
specified thread.
.TP 7
.B EPERM
The implementation does not allow the application to modify one of
the parameters to the value specified.
.TP 7
.B ESRCH
The value specified by \fIthread\fP does not refer to a existing thread.
.sp
.LP
These functions shall not return an error code of [EINTR].
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.LP
None.
.SH APPLICATION USAGE
.LP
None.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIpthread_setschedprio\fP() , \fIsched_getparam\fP() , \fIsched_getscheduler\fP()
, the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.h>\fP, \fI<sched.h>\fP
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .