HP-UX Reference (11i v1 00/12) - 2 System Calls (vol 5)

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rtsched(2) rtsched(2)

member in the param structure is any integer within the inclusive priority range for the current scheduling

policy of the process speciﬁed by pid.

Higher numerical values for the priority represent higher (stronger) priorities. Note that this is different

from the SCHED_HPUX , SCHED_TIMESHARE, SCHED_NOAGE , and SCHED_RTPRIO scheduling poli-

cies, where higher numerical values represent lower (weaker) priorities. See the

PRI_HPUX_TO_POSIX() and PRI_POSIX_TO_HPUX() functions, and SCHED_RTPRIO ,

SCHED_NOAGE , and SCHED_OTHER in "Scheduling Policies" below.

If a process described by pid exists and if the calling process has permission, the scheduling parameters are

set for the process whose process ID is equal to pid.

If pid is zero, the scheduling parameters are set for the calling process.

If the process pid contains more than one thread or lightweight process (that is, the process is multi-

threaded), this function shall only change the process scheduling policy and priority. Individual threads or

lightweight processes in the target process shall not have their scheduling policies and priorities modiﬁed.

Note that if the target process is multi-threaded, this process scheduling policy and priority change will

only affect a child process that is created later and inherits its parent’s scheduling policy and priority. The

priority returned is the old priority of the target process, though individual threads or lightweight processes

may have a different value if some other interface is used to change an individual thread or lightweight

processes priority.

Only a superuser may change the scheduling parameters of another process.

The calling process must have the appropriate privileges or be a member of a group having

PRIV_RTSCHED access to successfullycall sched_setparam()

The target process, whether it is running or not running, will resume execution after all other runnable

processes of equal or greater priority have been scheduled to run.

If the priority of the process speciﬁed by the pid argument is set higher than that of the lowest priority run-

ning process, and if the speciﬁed process is ready to run, the process speciﬁed by the pid argument will

preempt a lowest-priority running process. Similarly, if the process calling

sched_setparam() sets its

own priority lower than that of one or more other nonempty process lists, then the process that is the head

of the highest priority list will also preempt the calling process. Thus, in either case, the originating pro-

cess may not receive notiﬁcation of the completion of the requested priority change until the higher priority

process has executed.

sched_getparam()

The

sched_getparam() function returns the scheduling parameters of a process speciﬁed by pid in the

sched_param structure pointed to by param.

If a process described by pid exists, the scheduling parameters are returned for the process whose process

ID is equal to pid.

If the process pid contains more than one thread or lightweight process (that is, the process is multi-

threaded), this function shall only return the process scheduling policy and priority. Individual threads or

lightweight processes in the target process will have their own scheduling policies and priorities which may

be different from the scheduling policy and priority of their process.

If pid is zero, the scheduling parameters are returned for the calling process.

sched_setscheduler()

The

sched_setscheduler()

function sets the scheduling policy and scheduling parameters of the pro-

cess 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 can be any integer

within the inclusive priority range for the scheduling policy speciﬁed by policy.

The possible values for the policy parameter are deﬁned in the header ﬁle

<sched.h>, and mentioned

below.

If a process described by pid exists, the scheduling policy and scheduling parameters are 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.

If the process pid contains more than one thread or lightweight process (that is, the process is multi-

threaded), this function shall only change the process scheduling policy and priority. Individual threads or

lightweight processes in the target process shall not have their scheduling policies and priorities modiﬁed.

Section 2−−266 − 2 − HP-UX Release 11i: December 2000

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