PTHREAD_GETSCHEDPARAM(P) POSIX Programmer's Manual PTHREAD_GETSCHEDPARAM(P)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 speci‐
fied 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.
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_getschedparam() function may fail if:
ESRCH The value specified by thread does not refer to an existing
thread.
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.
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.
EPERM The caller does not have the appropriate permission 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.
ESRCH The value specified by thread does not refer to a existing
thread.
These functions shall not return an error code of [EINTR].
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOpthread_setschedprio() , sched_getparam() , sched_getscheduler() , the
Base Definitions volume of IEEE Std 1003.1-2001, <pthread.h>, <sched.h>
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 .
IEEE/The Open Group 2003 PTHREAD_GETSCHEDPARAM(P)
