PTHREAD_GETSCHEDPARAM(3P) POSIX Programmer's Manual PTHREAD_GETSCHEDPARAM(3P)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 schedul‐
ing 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 multi-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 implementation-defined.
The pthread_getschedparam() function shall retrieve the scheduling pol‐
icy and scheduling parameters for the thread whose thread ID is given
by thread and shall store those values in policy and param, respec‐
tively. 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
implementation-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 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 sched_ss_low_priority, sched_ss_repl_period,
sched_ss_init_budget, sched_priority, and sched_ss_max_repl. The spec‐
ified sched_ss_repl_period shall be greater than or equal to the speci‐
fied 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 suc‐
ceed; if not, the function shall fail. It is unspecified whether the
sched_ss_repl_period and sched_ss_init_budget values are stored as pro‐
vided by this function or are rounded to align with the resolution of
the clock being used.
If the pthread_setschedparam() function fails, the scheduling parame‐
ters 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 parame‐
ters 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 speci‐
fied 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 ALSOpthread_setschedprio(), sched_getparam(), sched_getscheduler()
The Base Definitions volume of POSIX.1‐2008, <pthread.h>, <sched.h>
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 Electri‐
cal 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.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 PTHREAD_GETSCHEDPARAM(3P)
