sched_setscheduler() 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 If pid is negative, the behavior of sched_setscheduler() is unspecified If a process specified by pid exists, and if the calling process has permission, the scheduling policy and scheduling parameters shall be set for the process whose process ID is equal to pid If pid is zero, the scheduling policy and scheduling parameters shall be set for the calling process The condition under which one process has the appropriate privilege to change the scheduling parameters of another process are implementation-defined Implementations may require that the requesting process have permission to set its own scheduling parameters or those of another process Implementation-defined restrictions may apply as to the appropriate privileges required to set a process' own scheduling policy, or another process' scheduling policy, to a particular value The sched_setscheduler() function shall be 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 The sched_ss_repl_period and sched_ss_init_budget members of the param argument shall represent the time parameters used by the sporadic server scheduling policy for the target process The sched_ss_max_repl member of the param argument shall represent the maximum number of replenishments that are allowed to be pending simultaneously for the process scheduled under this scheduling policy If the scheduling policy specified by policy is either SCHED_FIFO or SCHED_RR, the sched_ss_low_priority, sched_ss_repl_period, and sched_ss_init_budget members of the param argument shall have no effect on the scheduling behavior For threads with system scheduling contention scope, this function shall have no effect on their scheduling For threads with process scheduling contention scope, the threads' scheduling policy and associated parameters shall not be affected The underlying kernel-scheduled entities for the system contention scope threads shall not be affected by this function The underlying kernel-scheduled entities for the process contention scope threads shall have their scheduling policy and associated scheduling parameters changed to the values specified in policy and param, respectively Upon successful completion, the function shall return the former scheduling policy of the specified process If the sched_setscheduler() function fails to complete successfully, the policy and scheduling parameters shall remain unchanged If the sched_setscheduler() function fails to complete successfully, the function shall return a value of -1 The sched_setscheduler() function shall return EINVAL if the value of the policy parameter is invalid, or one or more of the parameters contained in param is outside the valid range for the specified scheduling policy The sched_setscheduler() function shall return EPERM if the requesting process does not have permission to set either or both of the scheduling parameters or the scheduling policy of the specified process The sched_setscheduler() function shall return ESRCH if no process can be found corresponding to that specified by pid Kernel-scheduled entities for use by process contention scope threads that are created after this call completes shall inherit their scheduling policy and associated scheduling parameters from the process