NAME    [Toc]    [Back]

       sched_setparam  -  Sets  the  scheduling parameters of the
       specified process (P1003.1b)

SYNOPSIS    [Toc]    [Back]

       #include <sched.h>

       int sched_setparam ( pid_t pid, const  struct  sched_param
       *param);

LIBRARY    [Toc]    [Back]

       Realtime Library (librt.so, librt.a)

PARAMETERS    [Toc]    [Back]

       Specifies  the  ID of the process whose scheduling parameters
 are set. If pid is zero, the scheduling parameters of
       the  calling  process  are  set.  Specifies a pointer to a
       sched_param  structure,  which  contains  the   scheduling
       parameters   of  the  specified  process.  Currently,  the
       sched_param structure contains only a priority field.  The
       value of the priority value is any integer within the priority
 range for the current scheduling policy of the  process
 specified by pid.

DESCRIPTION    [Toc]    [Back]

       The sched_setparam function changes the scheduling parameters
 of a process. Setting priorities such that  the  most
       critical  process has the highest priority allows applications
 to determine more effectively when  a  process  will
       run.

       At run time, a process starts out with an initial priority
       of SCHED_PRIO_USER_MAX.   A  call  to  the  sched_setparam
       function that raises the priority of a process also raises
       the maximum priority for the process. This higher  maximum
       priority  exists  for the life of the process or until the
       priority is set to a new, higher priority through  another
       call  to the sched_setparam function. The maximum priority
       cannot be adjusted downward, but subsequent calls  to  the
       sched_setparam or sched_setscheduler functions can specify
       that a process run at a lower priority.

       You must have superuser privileges  to  set  the  priority
       above  the  user maximum, SCHED_PRIO_USER_MAX. A superuser
       can set the priority outside the range  of  the  specified
       pid's scheduling policy.

       When  the  function  completes, the target process resumes
       execution after all other runnable processes of  equal  or
       greater  priority are scheduled to run. If the priority of
       the target process is set higher than that of the  calling
       process,  and  if the target process is ready to run, then
       the target process will preempt the  calling  process.  If
       the  calling  process set its own priority lower than some
       other process, then the other  process  will  preempt  the
       calling  process. In either situation, the calling process
       might not receive notification of the  completion  of  the
       requested  priority  change  until  the target process has
       executed.

       The scheduling parameters of the process as  indicated  by
       pid  are  obtained with a call to the sched_getparam function.


       The priority of a process is  inherited  across  fork  and
       exec calls.

RETURN VALUES    [Toc]    [Back]

       On  a  successful call to the sched_setparam function, the
       scheduling parameters are set and a value of 0  (zero)  is
       returned.  On  an  unsuccessful  call,  a  value  of -1 is
       returned and errno  is  set  to  indicate  that  an  error
       occurred and the priority is unchanged.

ERRORS    [Toc]    [Back]

       The sched_setparam function fails under the following conditions:
 One or more of the requested  scheduling  parameters
  is outside the range defined for the specified pid's
       scheduling policy.  This error does not  apply  for  superusers.
   The  requesting process does not have permission
       to set the scheduling parameters for  the  specified  process,
 nor does it have appropriate privilege to invoke the
       sched_setparam function.  No process can be  found  corresponding
 to that specified by pid.

SEE ALSO    [Toc]    [Back]

       Functions:  getpid(2),  sched_getparam(3), sched_getscheduler(3), sched_setscheduler(3)

       Guide to Realtime Programming



                                                sched_setparam(3)