PTHREAD_GETSCHEDPARAM(3)   POSIX Programmer's Manual  PTHREAD_GETSCHEDPARAM(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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 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.

       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.

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 1003.1-2017, 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/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017             PTHREAD_GETSCHEDPARAM(3)
