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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>


       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 .