trusty (3) pthread_setschedparam.3posix.gz

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 .