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SCHED_SETSCHEDULER(3P)     POSIX Programmer's Manual    SCHED_SETSCHEDULER(3P)
PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       sched_setscheduler -- set scheduling policy and parameters (REALTIME)
SYNOPSIS
       #include <sched.h>
       int sched_setscheduler(pid_t pid, int policy,
           const struct sched_param *param);
DESCRIPTION
       The sched_setscheduler() function shall set the scheduling  policy  and
       scheduling parameters of the process specified by pid to policy and the
       parameters specified in the sched_param structure pointed to by  param,
       respectively. The value of the sched_priority member in the sched_param
       structure shall be any integer within the inclusive priority range  for
       the scheduling policy specified by policy.  If the value of pid is neg-
       ative, the behavior of the sched_setscheduler()  function  is  unspeci-
       fied.
       The  possible  values  for  the  policy  parameter  are  defined in the
       <sched.h> header.
       If a process specified by pid exists, and if the  calling  process  has
       permission,  the  scheduling  policy and scheduling parameters shall be
       set for the process whose process ID is equal to pid.
       If pid is zero, the scheduling policy and scheduling  parameters  shall
       be set for the calling process.
       The  conditions  under  which one process has appropriate privileges to
       change the scheduling parameters of another process are implementation-
       defined.
       Implementations may require that the requesting process have permission
       to set its own scheduling  parameters  or  those  of  another  process.
       Additionally,  implementation-defined  restrictions may apply as to the
       appropriate privileges required to set the  scheduling  policy  of  the
       process,  or  the scheduling policy of another process, to a particular
       value.
       The sched_setscheduler() function shall be considered successful if  it
       succeeds  in setting the scheduling policy and scheduling parameters of
       the process specified by pid to the values specified by policy and  the
       structure pointed to by param, respectively.
       See  Scheduling Policies for a description on how this function affects
       the scheduling of the threads within the target process.
       If the  current  scheduling  policy  for  the  target  process  is  not
       SCHED_FIFO,  SCHED_RR, or SCHED_SPORADIC, the result is implementation-
       defined; this case includes the SCHED_OTHER policy.
       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. It is  unspecified  whether  the  sched_ss_repl_period  and
       sched_ss_init_budget  values are stored as provided by this function or
       are rounded to align with the resolution of the clock being used.
       This function is not atomic  with  respect  to  other  threads  in  the
       process. Threads may continue to execute while this function call is in
       the process of changing the scheduling policy and associated scheduling
       parameters  for  the  underlying  kernel-scheduled entities used by the
       process contention scope threads.
RETURN VALUE
       Upon successful completion, the function shall return the former sched-
       uling  policy  of  the  specified  process. If the sched_setscheduler()
       function fails to complete  successfully,  the  policy  and  scheduling
       parameters  shall  remain  unchanged,  and  the function shall return a
       value of -1 and set errno to indicate the error.
ERRORS
       The sched_setscheduler() function shall fail if:
       EINVAL The value of the policy parameter is invalid, or one or more  of
              the parameters contained in param is outside the valid range for
              the specified scheduling policy.
       EPERM  The requesting process does not have permission to set either or
              both  of  the  scheduling parameters or the scheduling policy of
              the specified process.
       ESRCH  No process can be found corresponding to that specified by pid.
       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       Scheduling Policies, sched_getparam(), sched_getscheduler(), sched_set-
       param()
       The Base Definitions volume of POSIX.1-2008, <sched.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/online.html .
       Any typographical or formatting errors that appear  in  this  page  are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors,  see  https://www.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013               SCHED_SETSCHEDULER(3P)