sched_setparam(3RT)					    Realtime Library Functions					       sched_setparam(3RT)

NAME

       sched_setparam - set scheduling parameters

SYNOPSIS

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

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

DESCRIPTION

       The  sched_setparam()  function	sets  the scheduling parameters of the process specified by pid to the values specified by the sched_param
       structure pointed to by param. The value of the sched_priority member in the sched_param structure is any integer within the inclusive pri-
       ority  range  for  the current scheduling policy of the process specified by pid. Higher numerical values for the priority represent higher
       priorities. If the value of pid is negative, the behavior of the sched_setparam() function is unspecified.

       If a process specified by pid exists and if the calling process has permission, the scheduling parameters will be 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 zero, the scheduling parameters will be set for the calling process.

       The target process, whether it is running or not running, resumes execution after all other runnable processes of equal or greater priority
       have been scheduled to run.

       If  the	priority  of  the  process specified by the pid argument is set higher than that of the lowest priority running process and if the
       specified process is ready to run, the process specified by the pid argument preempts a lowest priority running process. Similarly, if  the
       process	calling sched_setparam() sets its own priority lower than that of one or more other non-empty process lists, then the process that
       is the head of the highest priority list also preempts the calling process. Thus, in either case, the originating process might not receive
       notification of the completion of the requested priority change until the higher priority process has executed.

       If the current scheduling policy for the process specified by pid is not SCHED_FIFO or SCHED_RR, including SCHED_OTHER, the result is equal
       to priocntl(P_PID, pid, PC_SETPARMS, &pcparam), where pcparam is an image of *param.

       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 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.

       If an implementation supports a two-level scheduling model in which library threads are multiplexed on  top  of	several  kernel  scheduled
       entities, then 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 parameters changed to the
       value specified in param. 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 for the underlying kernel scheduled entities used by the process contention  scope
       threads.

RETURN VALUES

       If successful, the sched_setparam() function returns 0.

       If the call to sched_setparam() is unsuccessful, the priority remains unchanged, and the function returns -1 and sets errno to indicate the
       error.

ERRORS

       The sched_setparam() function will fail if:

       EINVAL	       One or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the  specified
		       pid.

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

       EPERM	       The  requesting	process  does  not have permission to set the scheduling parameters for the specified process, or does not
		       have the appropriate privilege to invoke sched_setparam().

       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

       intro(2), exec(2), librt(3LIB), sched.h(3HEAD), sched_getparam(3RT), sched_getscheduler(3RT), sched_setscheduler(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_setparam(3RT)