SCHED_SETSCHEDULER(3C) Standard C Library Functions SCHED_SETSCHEDULER(3C)

NAME

sched_setscheduler - set scheduling policy and scheduling parameters

SYNOPSIS

#include <sched.h>

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

DESCRIPTION

The sched_setscheduler() function 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 sched_param
structure is any integer within the inclusive priority range for the
scheduling policy specified by policy. The sched_setscheduler() function
ignores the other members of the sched_param structure. If the value of
pid is negative, the behavior of the sched_setscheduler() function is
unspecified.


The possible values for the policy parameter are defined in the header
<sched.h> (see sched.h(3HEAD)):


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 0. See Intro(2).


If pid is 0, the scheduling policy and scheduling parameters are set for
the calling process.


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.


The sched_setscheduler() function is considered successful if it succeeds
in setting the scheduling policy and scheduling parameters of the process
specified by pid to the values specified by policy and the structure
pointed to by param, respectively.

RETURN VALUES

Upon successful completion, the function returns the former scheduling
policy of the specified process. If the sched_setscheduler() function
fails to complete successfully, the policy and scheduling parameters
remain unchanged, and the function returns -1 and sets errno to indicate
the error.

ERRORS

The sched_setscheduler() function will fail if:

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.


EPERM
The requesting process does not have permission to set either
or both of the scheduling parameters or the scheduling policy
of the specified process.


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

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | MT-Safe |
+--------------------+-------------------+
|Standard | See standards(7). |
+--------------------+-------------------+

SEE ALSO

priocntl(1), Intro(2), exec(2), priocntl(2), sched_get_priority_max(3C),
sched_getparam(3C), sched_getscheduler(3C), sched_setparam(3C),
sched.h(3HEAD), librt(3LIB), attributes(7), standards(7)

November 26, 2017 SCHED_SETSCHEDULER(3C)