SCHED_SETSCHEDULER(2) BSD System Calls Manual SCHED_SETSCHEDULER(2)NAME
sched_setscheduler, sched_getscheduler — set/get scheduling policy and
scheduler parameters
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#include <sched.h>
int
sched_setscheduler(pid_t pid, int policy,
const struct sched_param *param);
int
sched_getscheduler(pid_t pid);
DESCRIPTION
The sched_setscheduler() function sets the scheduling policy and schedul‐
ing parameters of the process specified by pid to policy and the parame‐
ters specified in the sched_param structure pointed to by param, respec‐
tively. The value of the sched_priority member in the param structure
must be any integer within the inclusive priority range for the schedul‐
ing policy specified by policy.
In this implementation, if the value of pid is negative the function will
fail.
If a process specified by pid exists and if the calling process has per‐
mission, the scheduling policy and scheduling parameters will be set for
the process whose process ID is equal to pid.
If pid is zero, the scheduling policy and scheduling parameters are set
for the calling process.
In this implementation, the policy of when a process can affect the
scheduling parameters of another process is specified in IEEE Std
1003.1b-1993 (“POSIX.1”) as a write-style operation.
The scheduling policies are 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.
The sched_param structure is defined in <sched.h>:
struct sched_param {
int sched_priority; /* scheduling priority */
};
The sched_getscheduler() function returns the scheduling policy of the
process specified by pid.
If a process specified by pid exists and if the calling process has per‐
mission, the scheduling parameters for the process whose process ID is
equal to pid are returned.
In this implementation, the policy of when a process can obtain the
scheduling parameters of another process are detailed in IEEE Std
1003.1b-1993 (“POSIX.1”) as a read-style operation.
If pid is zero, the scheduling parameters for the calling process will be
returned. In this implementation, the sched_getscheduler function will
fail if pid is negative.
RETURN VALUES
Upon successful completion, the value 0 is returned; 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:
[ENOSYS] The system is not configured to support this function‐
ality.
[EPERM] The requesting process doesn not have permission as
detailed in IEEE Std 1003.1b-1993 (“POSIX.1”).
[ESRCH] No process can be found corresponding to that speci‐
fied by pid.
[EINVAL] The value of the policy parameter is invalid, or one
or more of the parameters contained in param is out‐
side the valid range for the specified scheduling pol‐
icy.
SEE ALSOsched_getparam(2), sched_get_priority_max(2), sched_get_priority_min(2),
sched_rr_get_interval(2), sched_setparam(2), sched_yield(2)STANDARDS
The sched_setscheduler() and sched_getscheduler() functions conform to
IEEE Std 1003.1b-1993 (“POSIX.1”).
BSD March 12, 1998 BSD
