NAME

sched_get_priority_max, sched_get_priority_min, sched_rr_get_interval —

get scheduling parameter limits

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <sched.h>

int
sched_get_priority_max(int policy);

int
sched_get_priority_min(int policy);

int
sched_rr_get_interval(pid_t pid, struct timespec *interval);

DESCRIPTION

The sched_get_priority_max() and sched_get_priority_min() system calls return the appropriate maximum or minimum, respectively, for the scheduling policy specified by policy. The sched_rr_get_interval() system call updates the timespec structure referenced by the interval argument to contain the current execution time limit (i.e., time quantum) for the process specified by pid. If pid is zero, the current execution time limit for the calling process is returned.

The value of policy should be one of the scheduling policy values defined in <sched.h>:

[SCHED_FIFO]: First-in-first-out fixed priority scheduling with no round robin scheduling;
[SCHED_OTHER]: The standard time sharing scheduler;
[SCHED_RR]: Round-robin scheduling across same priority processes.

RETURN VALUES

If successful, the sched_get_priority_max() and sched_get_priority_min() system calls shall return the appropriate maximum or minimum values, respectively. If unsuccessful, they shall return a value of -1 and set errno to indicate the error.

The sched_rr_get_interval() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

ERRORS

On failure errno will be set to the corresponding value:

[EINVAL]: The value of the policy argument does not represent a defined scheduling policy.
[ENOSYS]: The sched_get_priority_max(), sched_get_priority_min(), and sched_rr_get_interval() system calls are not supported by the implementation.
[ESRCH]: No process can be found corresponding to that specified by pid.

STANDARDS

The sched_get_priority_max(), sched_get_priority_min(), and sched_rr_get_interval() system calls conform to IEEE Std 1003.1b-1993 (“POSIX.1b”).