sched_setparam() sets the scheduling parameters to the parameters specified in the sched_param structure pointed to by param Higher numerical values for the priority represent higher priorities If pid is negative, the behavior of sched_setparam() is unspecified 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 Implementations may require the requesting process to have the appropriate privilege to set its own scheduling parameters or those of another process The target process, whether it is running or not running, shall be moved to the tail of the thread list for its priority If the priority of the process specified by the pid argument is set higher than that of the lowest priority running process and if the specified process is ready to run, the process specified by the pid argument shall preempt a lowest priority running process If the process calling sched_setparam() sets its own priority lower than that of one or more other non-empty process lists, then the process that is the head of the highest priority list shall preempt the calling process The originating process might not receive notification of the completion of the requested priority change until the higher priority process has executed The sched_ss_repl_period and sched_ss_init_budget members of the param argument shall represent the time parameters to be 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 the SCHED_SPORADIC policy If the scheduling policy of the target process 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 If the scheduling policy of the target process is not SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the effects of the sched_ss_low_priority, sched_ss_repl_period, and sched_ss_init_budget members are implementation-defined (this case includes the SCHED_OTHER policy) If the current scheduling policy for the process specified by pid is not SCHED_FIFO, SCHED_RR or SCHED_SPORADIC, the result is implementation-defined; this case includes the SCHED_OTHER policy 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 parameters changed to the value specified in param 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 If successful, the sched_setparam() function shall return zero If the call to sched_setparam() is unsuccessful, the priority shall remain unchanged If the call to sched_setparam() is unsuccessful, the function shall return a value of -1 sched_setparam() sets errno == EINVAL when one or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the specified pid sched_setparam() sets errno == EPERM when the requesting process does not have permission to set the scheduling parameters for the specified process, or does not have the appropriate privilege to invoke schedparam() sched_setparam() sets errno == ESRCH when no process can be found corresponding to that specified by pid