How to set proper values for TThread Policy and Priority in Delphi 10.3 and Linux64 Compiler

Question

Within my Delphi Linux application I like to set a thread priority to "tpTimeCritical". Unfortunately the priority value cannot be changed. Every value <> 0 throws a Runtime Error 217.

I found out that on Linux the policy has to be changed first (SCHED_FIFO or SCHED_RR). In sched.h I have the following values:

#define SCHED_NORMAL    0
#define SCHED_FIFO      1
#define SCHED_RR        2
#define SCHED_BATCH     3
#define SCHED_IDLE      5
#define SCHED_DEADLINE  6

After the policy has been set correctly, the priority should be set to a value between 1 and 99. Unfortunately this does not work.

constructor TMyThread.Create;
begin
   inherited Create(True);

   Policy   := 1;
   Priority := 90;
end;

Answer 1

After my inquiry about this with Embarcadero (RSP-26280) it turned out to be a bug in the corresponding Linux thread implementation. The bug was fixed in June 2020 and the fix was included in the next official release (I think 10.4).