sched_setscheduler(3RT) Realtime Library Functions sched_setscheduler(3RT)NAMEsched_setscheduler - set scheduling policy and scheduling parameters
SYNOPSIS
cc [ flag... ] file... -lrt [ library... ]
#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 sched‐
uling 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() func‐
tion 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 suc‐
ceeds 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.
The effect of this function on individual threads is dependent on the
scheduling contention scope of the threads:
· For threads with system scheduling contention scope, these func‐
tions have no effect on their scheduling.
· For threads with process scheduling contention scope, the threads'
scheduling policy and associated parameters will not be affected.
However, the scheduling of these threads with respect to threads
in other processes may be dependent on the scheduling parameters
of their process, which are governed using these functions.
The underlying kernel scheduled entities for the process contention
scope threads will have their scheduling policy and associated schedul‐
ing parameters changed to the values specified in policy and param,
respectively. Kernel scheduled entities for use by process contention
scope threads that are created after this call completes inherit their
scheduling policy and associated scheduling parameters from the
process.
This function is not atomic with respect to other threads in the
process. Threads are allowed to continue to execute while this function
call is in the process of changing the scheduling policy and associated
scheduling parameters for the underlying kernel scheduled entities used
by the process contention scope threads.
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 paramenters
remain unchanged, and the function returns −1 and sets errno to indi‐
cate 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.
ENOSYS The sched_setscheduler() function is not supported by
the system.
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(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Interface Stability │Standard │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOpriocntl(1), intro(2), exec(2), priocntl(2), librt(3LIB),
sched.h(3HEAD), sched_get_priority_max(3RT), sched_getparam(3RT),
sched_getscheduler(3RT), sched_setparam(3RT), attributes(5)NOTES
Solaris 2.6 was the first release to support libposix4/librt. Prior to
this release, this function always returned −1 and set errno to ENOSYS.
SunOS 5.10 10 Aug 2006 sched_setscheduler(3RT)
