Re: All RTOS (linux Based ) Other than RT-Linux

Matt Giwer wrote:
The Natural Philosopher wrote:
Matt Giwer wrote:
mahi wrote:
Hi all, I want to know, there are any REAL TIME OPERATING
systems( RTOS) which should have total linux compatible other than RT-
Linux.
And are there any free Real time Operating systems ( Linux Based ) is
available on the Internet.
Please provide some information regarding this issue.
I have read that the kernel is interrupt driven rather than schedule driven. If that is what you mean, all linuxes are real time.

Thats not generally enough for many peoples definitions, which is that the time to respond to an (external) interrupt is fast, un blockable, and well defined.

I realize there are many definitions. However what you suggest is what "nice" is for. Having a real time OS and tailoring it are two different matters.


With respect, it isn't.

If you think of how many ways to stop your 'lunix' responding to a keyboard interrupt exist, you will get my drift.

Change the BIOS to no keyboard? Or something like that. The keyboard is not a linux function. It only reads the BIOS.


Shows how little you know..most ROM BIOSES are TOTALLY bypassed by linux. Their sole function is to get the OS in place with some form of basic keyboard and screen control. In case intervention is needed.

After that the interrupt routines are installed by the kernel for pretty much everything.


Most RTOSes are very lightweight and very carefully controlled in terms of response time to interrupts.

I have never become involved in tailoring a OS compile to single applications. I have no idea how to do it. I have READ killing all the unneeded material is possible.


Well it depends on what application you want to run..if its simple enough you probably wouldn't bother with an OS at all. Or you would write your own...it becomes less a question of what you remove that what you decide to include..you wouldn't need multiuser capabilities normally, though you might leave in a hierarchy of task priorities..you might not even need a strict multitasking ability. If the program does just one thing, that is processing some real time event and turning it into an output, you can leave the processor in either a halt state, or running in a null loop till an interrupt comes along.

Linux is a multiuser, multitasking general OS. Its not designed for real time work. People use it and work round that by stripping it down and having enough processor speed to cope with its deficiencies, and hoping no bug or unforeseen events slow it or crash it..but is not the best way to crack a real real-time application.

It's easier to buy in a proper RTOS with libc support and compile linux stuff to that..if you want REAL millisecond response times.

The problem with Linux as its stands is that lots of stuff inside the kernel may wait indeterminate times with most or all interrupts disabled, waiting for a peripheral to respond. Sure mostly this is engineered out for common cases: but there's plenty pf times that a buggy bit of code can freeze out the rest of the machine by hogging cycles or calling into the kernel to do something that doesn't complete in a timely fashion. Where defined response times are a matter of life and death - like in avionics, you will not find Linux.






.

Relevant Pages