sched_setscheduler(3RT) 				    Realtime Library Functions					   sched_setscheduler(3RT)

NAME

       sched_setscheduler - set scheduling policy and scheduling parameters

SYNOPSIS

       cc [ flag... ] file... -lrt [ library... ]
       #include <sched.h>

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

DESCRIPTION

       The  sched_setscheduler()  function  sets 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 is any integer within the inclusive priority range for the scheduling policy specified by policy. The sched_setsched-
       uler() function ignores the other members  of  the  sched_param	structure.  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 header <sched.h> (see sched.h(3HEAD)):

       If a process specified by pid exists and if the calling process has permission, the scheduling policy and scheduling parameters are set for
       the process whose process  ID is equal to pid. The real or effective user  ID of the calling process must match the  real  or  saved  (from
       exec(2)) user  ID of the target process unless the effective user  ID of the calling process is 0. See intro(2).

       If pid is 0, the scheduling policy and scheduling parameters are set for the calling process.

       To  change  the policy of any process to either of the real time policies  SCHED_FIFO or SCHED_RR, the calling process must either have the
       SCHED_FIFO or SCHED_RR policy or have an effective user ID of 0.

       The sched_setscheduler() function is 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.

       The effect of this function on individual threads is dependent on the scheduling contention scope of the threads:

	 o  For threads with system scheduling contention scope, these functions have no effect on their scheduling.

	 o  For  threads  with process scheduling contention scope, the threads' scheduling policy and associated parameters will not be affected.
	    However, the scheduling of these threads with respect to threads in other processes may be dependent on the scheduling  parameters	of
	    their process, which are governed using these functions.

       The  system supports a two-level scheduling model in which library threads are multiplexed on top of several kernel scheduled entities. The
       underlying kernel scheduled entities for the system contention scope threads will not be affected by these functions.

       The underlying kernel scheduled entities for the process contention scope threads will have their scheduling policy and associated schedul-
       ing  parameters	changed to the values specified in policy and param, respectively. Kernel scheduled entities for use by process contention
       scope threads that are created after this call completes inherit their scheduling policy and  associated  scheduling  parameters  from  the
       process.

       This  function  is  not atomic with respect to other threads in the process. Threads are allowed to 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 VALUES

       Upon  successful  completion, the function returns the former scheduling policy of the specified process. If the sched_setscheduler() func-
       tion fails to complete successfully, the policy and scheduling paramenters remain unchanged, and the function returns -1 and sets errno	to
       indicate the error.

ERRORS

       The sched_setscheduler() function will fail if:

       EINVAL	       The  value  of  policy  is  invalid, or one or more of the parameters contained in param is outside the valid range for the
		       specified scheduling policy.

       ENOSYS	       The sched_setscheduler() function is not supported by the system.

       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.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       priocntl(1), intro(2), exec(2), priocntl(2), librt(3LIB), sched.h(3HEAD), sched_get_priority_max(3RT), sched_getparam(3RT), sched_getsched-
       uler(3RT), sched_setparam(3RT), attributes(5)

NOTES

       Solaris 2.6 was the first release to support libposix4/librt. Prior to this release, this function always returned  -1  and  set  errno	to
       ENOSYS.

SunOS 5.10							    5 Oct 2001						   sched_setscheduler(3RT)