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SCHED_SETSCHEDULER(2) | 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¶
Thesched_setscheduler
() system call 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
param structure must be any integer within
the inclusive priority range for the scheduling policy specified by
policy.
In this implementation, if the value of pid is
negative the system call will fail.
If a process specified by pid exists and if the
calling process has permission, 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.1b”) 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.
struct sched_param { int sched_priority; /* scheduling priority */ };
sched_getscheduler
() system call returns
the scheduling policy of the process specified by
pid.
If a process specified by pid exists and if the
calling process has permission, 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.1b”) 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 system call 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 functionality.
- [
EPERM
] - The requesting process doesn not have permission as detailed in IEEE Std 1003.1b-1993 (“POSIX.1b”).
- [
ESRCH
] - No process can be found corresponding to that specified by pid.
- [
EINVAL
] - The value of the policy argument is invalid, or one or more of the parameters contained in param is outside the valid range for the specified scheduling policy.
SEE ALSO¶
sched_getparam(2), sched_get_priority_max(2), sched_get_priority_min(2), sched_rr_get_interval(2), sched_setparam(2), sched_yield(2)STANDARDS¶
Thesched_setscheduler
() and
sched_getscheduler
() system calls conform
to IEEE Std 1003.1b-1993
(“POSIX.1b”).March 12, 1998 | Debian |