set_rt_thread_priority

This function sets the operating system scheduling priority that the library uses to receive real-time data and run real-time callbacks. The setting applies from the next connect_rt_control. Without this call, the library uses the operating system’s default scheduling.

Definition
DRFLEx.h within class CDRFLEx, public section

bool set_rt_thread_priority(int nPolicy, int nPriority) { return _set_rt_thread_priority(_rbtCtrlUDP, nPolicy, nPriority); };

Parameter

Parameter Name	Data Type	Description
nPolicy	int	Scheduling policy. Linux: `SCHED_FIFO`, `SCHED_RR` or `SCHED_OTHER`. Windows: `0`. `-1` restores the default scheduling on both systems.
nPriority	int	Scheduling priority. Linux: with `SCHED_FIFO` or `SCHED_RR`, a value from `sched_get_priority_min` to `sched_get_priority_max` for that policy (1 to 99); with `SCHED_OTHER`, `0`. Windows: a `THREAD_PRIORITY_*` level: `THREAD_PRIORITY_IDLE` (-15), `THREAD_PRIORITY_LOWEST` (-2), `THREAD_PRIORITY_BELOW_NORMAL` (-1), `THREAD_PRIORITY_NORMAL` (0), `THREAD_PRIORITY_ABOVE_NORMAL` (1), `THREAD_PRIORITY_HIGHEST` (2) or `THREAD_PRIORITY_TIME_CRITICAL` (15). Ignored when `nPolicy` is `-1`.

Return

Value	Description
1	The setting is stored and applies from the next connect_rt_control.
0	Nothing changed. Real-time control is connected, the policy or priority is not valid, or (Linux) the process is not allowed to use the requested real-time priority. For an invalid or disallowed value, the library prints the reason to standard error.

Caution

Call this function before connect_rt_control or after disconnect_rt_control. While real-time control is connected, it returns 0.
If the priority cannot be applied when connect_rt_control runs, connect_rt_control returns 0 and closes the real-time connection.
On Linux, SCHED_FIFO and SCHED_RR need permission to use real-time scheduling: the CAP_SYS_NICE capability, or an RLIMIT_RTPRIO limit of at least nPriority (for example set with ulimit -r).

Example

#include <sched.h>

// Receive RT data and run RT callbacks at SCHED_FIFO priority 80 (Linux).
if (!drfl.set_rt_thread_priority(SCHED_FIFO, 80)) {
    printf("SCHED_FIFO 80 is not available.\n");
}
if (drfl.connect_rt_control("192.168.137.100", 12347)) {
    drfl.start_rt_control();
}

In this example, the priority is set before the RT channel is connected, so it applies to that connection.

Tips

Use set_rt_thread_priority(-1, 0) to return to the default scheduling for the next connection.