PTHREAD_GETSCHEDPARAM
Section: POSIX Programmer's Manual (3P)
Updated: 2017
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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.
NAME
pthread_getschedparam,
pthread_setschedparam
- dynamic thread scheduling parameters access
(
REALTIME THREADS)
SYNOPSIS
#include <pthread.h>
int pthread_getschedparam(pthread_t thread, int *restrict policy,
struct sched_param *restrict param);
int pthread_setschedparam(pthread_t thread, int policy,
const struct sched_param *param);
DESCRIPTION
The
pthread_getschedparam()
and
pthread_setschedparam()
functions shall, respectively, get and set the scheduling policy and
parameters of individual threads within a mult-threaded process to be
retrieved and set. For SCHED_FIFO and SCHED_RR,
the only required member of the
sched_param
structure is the priority
sched_priority.
For SCHED_OTHER,
the affected scheduling parameters are implementatio-defined.
The
pthread_getschedparam()
function shall retrieve the scheduling policy and scheduling parameters
for the thread whose thread ID is given by
thread
and shall store those values in
policy
and
param,
respectively. The priority value returned from
pthread_getschedparam()
shall be the value specified by the most recent
pthread_setschedparam(),
pthread_setschedprio(),
or
pthread_create()
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
pthread_setschedparam()
function shall set the scheduling policy and associated scheduling
parameters for the thread whose thread ID is given by
thread
to the policy and associated parameters provided in
policy
and
param,
respectively.
The
policy
parameter may have the value SCHED_OTHER, SCHED_FIFO, or SCHED_RR. The
scheduling parameters for the SCHED_OTHER policy are
implementatio-defined. The SCHED_FIFO and SCHED_RR policies shall
have a single scheduling parameter,
priority.
If _POSIX_THREAD_SPORADIC_SERVER is defined, then the
policy
argument may have the value SCHED_SPORADIC, with the exception for the
pthread_setschedparam()
function that if the scheduling policy was not SCHED_SPORADIC at the
time of the call, it is implementatio-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
sched_ss_low_priority,
sched_ss_repl_period,
sched_ss_init_budget,
sched_priority,
and
sched_ss_max_repl.
The specified
sched_ss_repl_period
shall be greater than or equal to the specified
sched_ss_init_budget
for the function to succeed; if it is not, then the function shall
fail. The value of
sched_ss_max_repl
shall be within the inclusive range [1,{SS_REPL_MAX}]
for the function to succeed; if not, the function shall fail.
It is unspecified whether the
sched_ss_repl_period
and
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.
If the
pthread_setschedparam()
function fails, the scheduling parameters shall not be changed
for the target thread.
RETURN VALUE
If successful, the
pthread_getschedparam()
and
pthread_setschedparam()
functions shall return zero; otherwise, an error number shall be
returned to indicate the error.
ERRORS
The
pthread_setschedparam()
function shall fail if:
- ENOTSUP
-
An attempt was made to set the policy or scheduling parameters to an
unsupported value.
- ENOTSUP
-
An attempt was made to dynamically change the scheduling policy to
SCHED_SPORADIC, and the implementation does not support this change.
The
pthread_setschedparam()
function may fail if:
- EINVAL
-
The value specified by
policy
or one of the scheduling parameters associated with the scheduling
policy
policy
is invalid.
- EPERM
-
The caller does not have appropriate privileges to set either the
scheduling parameters or the scheduling policy of the specified
thread.
- EPERM
-
The implementation does not allow the application to modify
one of the parameters to the value specified.
These functions shall not return an error code of
[EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
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
[ESRCH]
error.
FUTURE DIRECTIONS
None.
SEE ALSO
pthread_setschedprio(),
sched_getparam(),
sched_getscheduler()
The Base Definitions volume of POSIX.1-2017,
<pthread.h>,
<sched.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.-2017, Standard for Information Technology- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 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 .
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/ma-pages/reporting_bugs.html .
Index
- PROLOG
-
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- EXAMPLES
-
- APPLICATION USAGE
-
- RATIONALE
-
- FUTURE DIRECTIONS
-
- SEE ALSO
-
- COPYRIGHT
-
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