NAME

       pthread_setschedprio - dynamic thread scheduling parameters access (REALTIME THREADS)

SYNOPSIS

       #include <pthread.h>

       int pthread_setschedprio(pthread_t thread, int prio);

DESCRIPTION

       The  pthread_setschedprio()  function shall set the scheduling priority for the thread whose thread ID is
       given by thread to the value given by prio. See  Scheduling  Policies  for  a  description  on  how  this
       function call affects the ordering of the thread in the thread list for its new priority.

       If  the  pthread_setschedprio() function fails, the scheduling priority of the target thread shall not be
       changed.

RETURN VALUE

       If successful, the pthread_setschedprio() function shall return zero; otherwise, an error number shall be
       returned to indicate the error.

ERRORS

       The pthread_setschedprio() function may fail if:

       EINVAL The value of prio is invalid for the scheduling policy of the specified thread.

       ENOTSUP
              An attempt was made to set the priority to an unsupported value.

       EPERM  The caller does not have the appropriate permission to set the scheduling policy of the  specified
              thread.

       EPERM  The implementation does not allow the application to modify the priority to the value specified.

       ESRCH  The value specified by thread does not refer to an existing thread.

       The pthread_setschedprio() function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       The  pthread_setschedprio()  function provides a way for an application to temporarily raise its priority
       and then lower it again, without having the undesired side effect of yielding to  other  threads  of  the
       same  priority.  This  is  necessary  if  the application is to implement its own strategies for bounding
       priority inversion, such as priority inheritance or priority ceilings.   This  capability  is  especially
       important  if  the  implementation  does  not  support  the Thread Priority Protection or Thread Priority
       Inheritance options, but even if those options are supported it is needed if the application is to  bound
       priority inheritance for other resources, such as semaphores.

       The  standard  developers considered that while it might be preferable conceptually to solve this problem
       by modifying the specification of pthread_setschedparam(), it was too late to  make  such  a  change,  as
       there may be implementations that would need to be changed.  Therefore, this new function was introduced.

FUTURE DIRECTIONS

       None.

SEE ALSO

       Scheduling  Policies  ,  pthread_getschedparam()  ,  the Base Definitions volume of IEEE Std 1003.1-2001,
       <pthread.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_SETSCHEDPRIO(P)