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 .

IEEE/The Open Group                                   2003                              PTHREAD_GETSCHEDPARAM(P)