SCHED_SETSCHEDULER(3)      POSIX Programmer's Manual     SCHED_SETSCHEDULER(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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
       negative, the behavior of the sched__setscheduler() function is
       unspecified.

       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
       scheduling 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__setparam()

       The Base Definitions volume of POSIX.1-2017, <sched.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                SCHED_SETSCHEDULER(3)
