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.TH PTHREAD_GETSCHEDPARAM "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_getschedparam,

pthread_setschedparam

\(em dynamic thread scheduling parameters access

(\fBREALTIME THREADS\fP)

.SH SYNOPSIS

.LP

.nf

#include <pthread.h>

.P

int pthread_getschedparam(pthread_t \fIthread\fP, int *restrict \fIpolicy\fP,

    struct sched_param *restrict \fIparam\fP);

int pthread_setschedparam(pthread_t \fIthread\fP, int \fIpolicy\fP,

    const struct sched_param *\fIparam\fP);

.fi

.SH DESCRIPTION

The

\fIpthread_getschedparam\fR()

and

\fIpthread_setschedparam\fR()

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

.BR sched_param

structure is the priority

.IR sched_priority .

For SCHED_OTHER,

the affected scheduling parameters are implementation-defined.

.P

The

\fIpthread_getschedparam\fR()

function shall retrieve the scheduling policy and scheduling parameters

for the thread whose thread ID is given by

.IR thread

and shall store those values in

.IR policy

and

.IR param ,

respectively. The priority value returned from

\fIpthread_getschedparam\fR()

shall be the value specified by the most recent

\fIpthread_setschedparam\fR(),

\fIpthread_setschedprio\fR(),

or

\fIpthread_create\fR()

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\fR()

function shall set the scheduling policy and associated scheduling

parameters for the thread whose thread ID is given by

.IR thread

to the policy and associated parameters provided in

.IR policy

and

.IR param ,

respectively.

.P

The

.IR policy

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,

.IR priority .

.P

If _POSIX_THREAD_SPORADIC_SERVER is defined, then the

.IR policy

argument may have the value SCHED_SPORADIC, with the exception for the

\fIpthread_setschedparam\fR()

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

.IR sched_ss_low_priority ,

.IR sched_ss_repl_period ,

.IR sched_ss_init_budget ,

.IR sched_priority ,

and

.IR sched_ss_max_repl .

The specified

.IR sched_ss_repl_period

shall be greater than or equal to the specified

.IR sched_ss_init_budget

for the function to succeed; if it is not, then the function shall

fail. The value of

.IR sched_ss_max_repl

shall be within the inclusive range [1,\c

{SS_REPL_MAX}]

for the function to succeed; if not, the function shall fail.

It is unspecified whether the

.IR sched_ss_repl_period

and

.IR sched_ss_init_budget

values are stored as provided by this function or are rounded to

align with the resolution of the clock being used.

.P

If the

\fIpthread_setschedparam\fR()

function fails, the scheduling parameters shall not be changed

for the target thread.

.SH "RETURN VALUE"

If successful, the

\fIpthread_getschedparam\fR()

and

\fIpthread_setschedparam\fR()

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

returned to indicate the error.

.SH ERRORS

The

\fIpthread_setschedparam\fR()

function shall fail if:

.TP

.BR ENOTSUP

An attempt was made to set the policy or scheduling parameters to an

unsupported value.

.TP

.BR ENOTSUP

An attempt was made to dynamically change the scheduling policy to

SCHED_SPORADIC, and the implementation does not support this change.

.P

The

\fIpthread_setschedparam\fR()

function may fail if:

.TP

.BR EINVAL

The value specified by

.IR policy

or one of the scheduling parameters associated with the scheduling

policy

.IR policy

is invalid.

.TP

.BR EPERM

The caller does not have appropriate privileges to set either the

scheduling parameters or the scheduling policy of the specified

thread.

.TP

.BR EPERM

The implementation does not allow the application to modify

one of the parameters to the value specified.

.P

These functions 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

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 "\fIpthread_setschedprio\fR\^(\|)",

.IR "\fIsched_getparam\fR\^(\|)",

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

.P

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

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

.IR "\fB<sched.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 .