sched_setparam

Synopsis

#include <sched.h>

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

Status

Implemented

Conformance

IEEE Std 1003.1-2017

Description

The sched_setparam() function shall set the scheduling parameters of the process specified by pid to the values specified by the sched_param structure pointed to by param. The value of the sched_priority member in the sched_param structure shall be 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 priorities. The priority range of SCHED_RR, the only policy supported by Phoenix-RTOS, is returned by sched_get_priority_min() and sched_get_priority_max(), see Scheduling priorities. If the value of pid is negative, the behavior of the sched_setparam() function is unspecified; Phoenix-RTOS returns -1 and sets errno to EINVAL.

If a process specified by pid exists, and if the calling process has permission, the scheduling parameters shall be set for the process whose process ID is equal to pid.

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

The conditions under which one process has permission to change the scheduling parameters of another process are implementation-defined. Phoenix-RTOS does not restrict changing the scheduling parameters of other processes.

This function is not atomic with respect to other threads in the process. Threads may continue to execute while this function call is in the process of changing the scheduling policy for the underlying kernel-scheduled entities used by the process contention scope threads.

Return value

If successful, the sched_setparam() function shall return zero.

If the call to sched_setparam() is unsuccessful, the priority shall remain unchanged, and the function shall return a value of -1 and set errno to indicate the error.

Errors

The sched_setparam() function shall fail if:

• EINVAL - One or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the specified pid.

• EPERM - The requesting process does not have permission to set the scheduling parameters for the specified process, or does not have appropriate privileges to invoke sched_setparam().

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

POSIX deviations

No POSIX deviations discovered.