.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "PTHREAD_SETSCHEDPRIO" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" pthread_setschedprio 
.SH NAME
pthread_setschedprio \- dynamic thread scheduling parameters access
(\fBREALTIME THREADS\fP)
.SH SYNOPSIS
.LP
\fB#include <pthread.h>
.br
.sp
int pthread_setschedprio(pthread_t\fP \fIthread\fP\fB, int\fP \fIprio\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIpthread_setschedprio\fP() function shall set the scheduling
priority for the thread whose thread ID is given by
\fIthread\fP to the value given by \fIprio\fP. See \fIScheduling Policies\fP
for a description on how this function call affects the ordering of
the thread in the thread list for its new priority.
.LP
If the \fIpthread_setschedprio\fP() function fails, the scheduling
priority of the target thread shall not be changed.
.SH RETURN VALUE
.LP
If successful, the \fIpthread_setschedprio\fP() function shall return
zero; otherwise, an error number shall be returned to
indicate the error.
.SH ERRORS
.LP
The \fIpthread_setschedprio\fP() function may fail if:
.TP 7
.B EINVAL
The value of \fIprio\fP is invalid for the scheduling policy of the
specified thread.
.TP 7
.B ENOTSUP
An attempt was made to set the priority to an unsupported value.
.TP 7
.B EPERM
The caller does not have the appropriate permission to set the scheduling
policy of the specified thread.
.TP 7
.B EPERM
The implementation does not allow the application to modify the priority
to the value specified.
.TP 7
.B ESRCH
The value specified by \fIthread\fP does not refer to an existing
thread.
.sp
.LP
The \fIpthread_setschedprio\fP() function 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
The \fIpthread_setschedprio\fP() function provides a way for an application
to temporarily raise its priority and then lower it
again, without having the undesired side effect of yielding to other
threads of the same priority. This is necessary if the
application is to implement its own strategies for bounding priority
inversion, such as priority inheritance or priority ceilings.
This capability is especially important if the implementation does
not support the Thread Priority Protection or Thread Priority
Inheritance options, but even if those options are supported it is
needed if the application is to bound priority inheritance for
other resources, such as semaphores.
.LP
The standard developers considered that while it might be preferable
conceptually to solve this problem by modifying the
specification of \fIpthread_setschedparam\fP(), it was too late to
make such
a change, as there may be implementations that would need to be changed.
Therefore, this new function was introduced.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIScheduling Policies\fP , \fIpthread_getschedparam\fP() , the Base
Definitions volume of IEEE\ Std\ 1003.1-2001, \fI<pthread.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 .