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



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

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_setsched-
       prio(),  or pthread_create() call affecting the target thread. It shall not reflect any temporary adjustments to its pri-
       ority 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 param-
       eter, priority.

       If _POSIX_THREAD_SPORADIC_SERVER is defined, then the policy argument may have the value SCHED_SPORADIC, with the  excep-
       tion  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_bud-
       get 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 pol-
              icy 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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                     PTHREAD_GETSCHEDPARAM(3P)