The Open Group Base Specifications Issue 7, 2018 edition
IEEE Std 1003.1-2017 (Revision of IEEE Std 1003.1-2008)
pthread_getschedparam, pthread_setschedparam - dynamic thread scheduling parameters access (
REALTIME
THREADS
)
[
TPS
]
![[Option Start]](../images/opt-start.gif)
#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
);
![[Option End]](../images/opt-end.gif)
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 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 implementation-defined. The SCHED_FIFO and SCHED_RR policies shall have a single scheduling parameter,
priority
.
[
TSP
]
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 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.
If successful, the
pthread_getschedparam
() and
pthread_setschedparam
() functions shall return zero; otherwise, an
error number shall be returned to indicate the error.
The
pthread_setschedparam
() function shall fail if:
[ENOTSUP]
An attempt was made to set the policy or scheduling parameters to an unsupported value.
[ENOTSUP]
[
TSP
]
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.
None.
None.
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.
None.
pthread_setschedprio
,
sched_getparam
,
sched_getscheduler
XBD
<pthread.h>
,
<sched.h>
First released in Issue 5. Included for alignment with the POSIX Threads Extension.
The
pthread_getschedparam
() and
pthread_setschedparam
() functions are marked as part of the Threads and Thread
Execution Scheduling options.
The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Thread
Execution Scheduling option.
The Open Group Corrigendum U026/2 is applied, correcting the prototype for the
pthread_setschedparam
() function so that
its second argument is of type
int
.
The SCHED_SPORADIC scheduling policy is added for alignment with IEEE Std 1003.1d-1999.
The
restrict
keyword is added to the
pthread_getschedparam
() prototype for alignment with the
ISO/IEC 9899:1999 standard.
The Open Group Corrigendum U047/1 is applied.
IEEE PASC Interpretation 1003.1 #96 is applied, noting that priority values can also be set by a call to the
pthread_setschedprio
()
function.
The
pthread_getschedparam
() and
pthread_setschedparam
() functions are marked only as part of the Thread Execution
Scheduling option as the Threads option is now part of the Base.
Austin Group Interpretation 1003.1-2001 #119 is applied, clarifying the accuracy requirements for the
sched_ss_repl_period
and
sched_ss_init_budget
values.
Austin Group Interpretation 1003.1-2001 #142 is applied, removing the [ESRCH] error condition.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0459 [314] is applied.
POSIX.1-2008, Technical Corrigendum 2, XSH/TC2-2008/0276 [757] is applied.
End of informative text.
