> Hell RTers
>
> I found the following paragraph at
> http://www.mysreenu.com/linux_software_design.html.
> Would someone please tell me whether the last sentence is correct. It was my
> understanding that anything running under Linux could be prempted by a RT
> scheduled task under RTLinux.
>
> Thanks,
> Daniel
>
> "Even with RTLinux/RTAI, it is generally the case that a real-time
> application will have tasks executing within user space. The issue then
> becomes the reliability of their performance. The behavior of all userspace
> programs, including daemons, may be important. In particular, if any user
> task other than your time-critical real-time task is making system calls,
> then that may delay your task."
that wrong - the user-space app can be delayed - and you could force priority
inversion by using badly designed synchronization between the RT-Task and the
non-RT-task but if the non-RT side does system calls that is irrelevant for
RT-performance. So as long as all time-critical steps are performed in the RT-modules
you are safe - any non-RT , and that is what this article is probably refering to as
"weil have tasks executing in user space" , like front end GUI's, may be delayed
indefinetly (atleast in theory).
this is true for RTL and RTAI so who ever wrote that article did not read the basic
docs of either.
hofrat
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