Re: insmod priority

Klemens Matthias Winkler wrote:

> Dear list,
> I am wondering what happens when running more than one real-time 
> Application on an RTLinux System. The second module is loaded by 
> executing the insmod command. Does the insmod process have a lower 
> priority than the already running real-time threads, or will it 
> preempt them? This might especially be a problem when the init_module 
> function needs much processing power. 

RTLinux uses normal Linux modules. That means that everything done in 
init_module will be executed in Linux kernel space (non-RT). Thats why 
you can use normal Linux functions in init_module to initialize your 
device or applications. Only when you call pthread_create a new RT-Task 
will be registered.

>
> Another thing I am not sure about are the fifo handlers. Is the 
> handler called when all real-time threads are idle, or will it preempt 
> them?


There are two different RTF handlers available. rtf_rt_handlers are 
called every time a RT task writes to or reads from an RTFIFO. If you 
look at the sources (rtlinux/fifos/rtl_fifo.c) it is called at the end 
of rtf_get, rtf_put which are used by RT tasks to access RTFIFOs.

The other type are rtf_handlers which are called by user-space processes 
when accessing RTFIFOs. They are called at the end of rtf_read and 
rtf_write which are the Linux fileoperations for the RTFIFO device-files.

To come back to your question after the FIFO handler is registered it is 
part of the read/write command of the rt-process or the 
user-space-process respectively. So the process the executes the 
read/write will not be preempted by the handler, but the handler is 
called on behalf of the process.

FloB


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