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)