[Rtai] system call

[Paolo Mantegazza]

??? wrote:
> hello,
> 
> When calling a rtai system call such as rt_task_init_schmod() in user space,
> it executes system call int $0xF6. After the execution of soft interrupt,
> which fuction does it execute. Because of curiosity, I want to known the
> machanism of rtai.
> 
> Can anyone tell me? Thanks very much!  
> 
> 

It goes to:
asmlinkage int rtai_syscall_dispatcher(struct pt_regs regs)
in hal.immed.

It is in the core abstraction layer because it can serve both RTAI own 
srqs (no RTAI scheduler implied necessarely, i.e. interrupts only real 
time) and RTAI services implying an RTAI scheduler.

Notice that you can enter RTAI through the standard Linux syscall also, 
implying a little overhead more. It is  a configuration options.
Such an option has been kept for i386 only, because RTAI is used on 486s 
and low end Pentiums, for which it is still worth caring of a small 
gain. On nowadays GHz machines it makes a negligible difference and in 
fact RTAI for x86_64 uses the Linux path only.

Paolo.


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