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.

       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_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 parameters 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 ALSO

       pthread_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 .