NAME

sched_setscheduler, sched_getscheduler − set/get scheduling policy and scheduling parameters

SYNOPSIS

cc [ flag ... ] file ... −lposix4 [ library ... ]

#include <sched.h>

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

int sched_getscheduler(pid_t pid);

struct sched_param {
intsched_priority;   /∗ process execution scheduling priority ∗/
...
}

MT-LEVEL

MT-Safe

DESCRIPTION

sched_setscheduler() 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 param->sched_priority must be any integer within the inclusive priority range for the scheduling policy specified by policy. 

The possible values for the policy parameter are defined in the header file <sched.h>:
SCHED_FIFO, SCHED_RR, or SCHED_OTHER.

If pid is zero, the scheduling policy and scheduling parameters are set for the calling process.  Otherwise, 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 super-user. See intro(2). 

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. 

sched_getscheduler() returns  the scheduling policy of the process specified by pid.  If pid is zero, the scheduling policy is returned for the calling process.  Otherwise, if a process specified by pid exists and if the calling process has permission, the scheduling policy is returned for the process whose process ID is equal to pid. 

RETURN VALUES

If successful, sched_setscheduler() returns the former scheduling policy of the specified process (pid), which will be one of the following values:

SCHED_FIFO (realtime),

First-In-First-Out; processes scheduled to this policy, if not pre-empted by

a higher priority or interrupted by a signal, will proceed until completion. 

SCHED_RR (realtime),

Round-Robin; processes scheduled to this policy, if not pre-empted by a

higher priority or interrupted by a signal, will execute for a

time period, returned by sched_rr_get_interval(3R) or by the system. 

or

SCHED_OTHER (time-sharing). 

Otherwise, the policy and sheduling parameters remain unchanged, sched_setscheduler() returns -1, and sets errno to indicate the error condition.  If successful, sched_getscheduler() returns the scheduling policy of the specified processr; otherwise, it returns -1, and sets errno to indicate the error condition. 

ERRORS

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 sched_setscheduler() and sched_getscheduler() are not supported by this implementation. 

EPERM sched_setscheduler() does not have permission to set either or both of the scheduling parameters or the scheduling policy of the specified process. 

sched_getscheduler() does not have permission to determine the scheduling policy of the specified process. 

ESRCH No process can be found corresponding to that specified by pid. 

SEE ALSO

priocntl(1), intro(2), exec(2), priocntl(2), sched_get_priority_max(3R), sched_setparam(3R)

BUGS

In Solaris 2.5, these functions always return −1 and set errno to ENOSYS, because this release does not support the Priority Scheduling option.  It is our intention to provide support for these interfaces in future releases. 

SunOS 5.5/SPARC  —  Last change: 16 Aug 1993