rtsched.2 (2010 09)

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rtsched(2) rtsched(2)

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 pro-

cess 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 mul-

tithreaded), this function will affect the policy and priority of individual kernel schedulable entities in the

process depending on their scheduling contention scope.

• For threads created with system contention scope, this system call will have no effect on their

scheduling or the scheduling of the underlying kernel scheduled entities.

• For threads with process contention scope, the threads’ scheduling parameters will not be affected.

However, the underlying kernel scheduled entities for the process contention scope threads will

have their scheduling parameters changed to the value speciﬁed in param. Kernel scheduled enti-

ties 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.

The priority returned is the old priority of the target process, though an individual thread or lightweight

process may have a different value if some other interface is used to change individual thread’s or light-

weight process’s priority.

The

OWNER privilege is required to change the scheduling parameters of another process.

The calling process must have the

RTSCHED privilege to successfully call sched_setscheduler()

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 param , respectively.

sched_getscheduler()

The

sched_getscheduler()

function returns the scheduling policy of the process speciﬁed by pid .

The values that can be returned by

sched_getscheduler()

are deﬁned in the header ﬁle

<sched.h> (see sched_setscheduler()

If a process described by pid exists, the scheduling policy is returned for the process whose process ID is

equal to pid.

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

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

tithreaded), 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.

sched_yield()

The

sched_yield() function forces the calling thread to relinquish the processor until it again

becomes the head of its thread list. It takes no arguments.

sched_get_priority_max(), sched_get_priority_min()

The

sched_get_priority_max() and sched_get_priority_min()

functions return the

appropriate maximum or minimum, respectively, for the scheduling policy speciﬁed by policy .

The value of policy must be one of the scheduling policy values deﬁned in

<sched.h>.

sched_rr_get_interval()

The

sched_rr_get_interval() function updates the timespec structure referenced by the interval

argument to contain the current execution time limit (that is, time quantum) for the process indicated by

pid under the SCHED_RR policy, at which a scheduling decision will be made when another process at

the same priority is ready to execute. If pid is zero, the current execution time limit for the calling pro-

cess is returned.

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