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.TH PTHREAD_SETSCHEDPRIO "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH PROLOG

This manual page is part of the POSIX Programmer's Manual.

The Linux implementation of this interface may differ (consult

the corresponding Linux manual page for details of Linux behavior),

or the interface may not be implemented on Linux.

.SH NAME

pthread_setschedprio

\(em dynamic thread scheduling parameters access

(\fBREALTIME THREADS\fR)

.SH SYNOPSIS

.LP

.nf

#include <pthread.h>

.P

int pthread_setschedprio(pthread_t \fIthread\fP, int \fIprio\fP);

.fi

.SH DESCRIPTION

The

\fIpthread_setschedprio\fR()

function shall set the scheduling priority for the thread whose thread

ID is given by

.IR thread

to the value given by

.IR prio .

See

.IR "Scheduling Policies"

for a description on how this function call affects the ordering of the

thread in the thread list for its new priority.

.P

If the

\fIpthread_setschedprio\fR()

function fails, the scheduling priority of the target thread shall not

be changed.

.SH "RETURN VALUE"

If successful, the

\fIpthread_setschedprio\fR()

function shall return zero; otherwise, an error number shall be

returned to indicate the error.

.SH ERRORS

The

\fIpthread_setschedprio\fR()

function may fail if:

.TP

.BR EINVAL

The value of

.IR prio

is invalid for the scheduling policy of the specified thread.

.TP

.BR EPERM

The caller does not have appropriate privileges to set the scheduling

priority of the specified thread.

.P

The

\fIpthread_setschedprio\fR()

function shall not return an error code of

.BR [EINTR] .

.LP

.IR "The following sections are informative."

.SH EXAMPLES

None.

.SH "APPLICATION USAGE"

None.

.SH RATIONALE

The

\fIpthread_setschedprio\fR()

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.

.P

The standard developers considered that while it might be preferable

conceptually to solve this problem by modifying the specification of

\fIpthread_setschedparam\fR(),

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.

.P

If an implementation detects use of a thread ID after the end of its

lifetime, it is recommended that the function should fail and report an

.BR [ESRCH] 

error.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "Scheduling Policies",

.IR "\fIpthread_getschedparam\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<pthread.h>\fP"

.SH COPYRIGHT

Portions of this text are reprinted and reproduced in electronic form

from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology

-- Portable Operating System Interface (POSIX), The Open Group Base

Specifications Issue 7, Copyright (C) 2013 by the Institute of

Electrical and Electronics Engineers, Inc and The Open Group.

(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .

Any typographical or formatting errors that appear

in this page are most likely

to have been introduced during the conversion of the source files to

man page format. To report such errors, see

https://www.kernel.org/doc/man-pages/reporting_bugs.html .