PTHREAD_SETSCHEDPRIO(3P)                            POSIX Programmer's Manual                           PTHREAD_SETSCHEDPRIO(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_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  pri-
       ority  ceilings.  This capability is especially important if the implementation does not support the Thread Priority Pro-
       tection 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,  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_SETSCHEDPRIO(3P)