All RTOS (linux Based ) Other than RT-Linux - Setup

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  1. All RTOS (linux Based ) Other than RT-Linux

    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.


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

    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.
    >

    What do you understand by:

    Real time?
    Linux compatible?

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

    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.

    --
    The purpose of peace talks between Palestine and Israel is to prevent
    Palestine from ever being free of the Israel occupation.
    -- The Iron Webmaster, 3842
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  4. Re: All RTOS (linux Based ) Other than RT-Linux

    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.


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

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

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

    Matt Giwer 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.


    Real time systems typically guarantee some timing (interrupt
    latency...), so that processes can react on events in a timely manner.
    Furthermore the response on events has time constraints, i.e. a process
    must lower its priority, after doing the time critical event handling.
    This requires that *all* system processes behave accordingly, what's not
    normally the case in an preemptive multitasking system. A related
    requirement are memory-resident event handlers, separated somehow from
    the less critical swappable parts of an process.

    IMO these requirements cannot be satisfied with the public Linux code,
    and also cannot be introduced by simple patches to the kernel etc. sources.

    Some approaches make the Linux kernel simply an process, running under
    control of an new RT kernel. But then RT processes will have to
    communicate and cooperate with the RT kernel, so that they run more in
    parallel to the Linux kernel, instead of controlled by the Linux kernel.
    IMO it then is inevitable to split RT applications into an RT process,
    running under control of the RT kernel, and an non-RT process, running
    under control of the Linux kernel. One also might see the RT part as
    kind of a device or driver, interacting with the remaining part of the
    application.

    IMO it will be simpler to use some available RT system, and make it's
    ABI so Linux-compatible, that Linux applications can be installed into
    such a system. But then it might be easier to install a veritable Linux
    into a VM, hosted by the RT OS. See also: The Xen Project.

    DoDi

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

    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.

    > 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.

    > 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.

    --
    Republicans are more interested in protecting the president than the troops.
    -- The Iron Webmaster, 3839
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  7. 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.







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

    Matt Giwer wrote:

    >> 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.


    Actually, "nice" is for batch jobs vs interactive ones. Has nothing to do
    with interrupts.

    However, there are real-time extensions to Unix/Linux which allow fixed
    priorities, no swapping, task activation/resumption on specified interrupts,
    etc.. While not enough for "hard" real time with rapid responses, the
    extensions are more than adequate for the average process control or SCADA
    system. One of the projects I was involved in ran an aluminum smelter SCADA
    system. It's been installed in several smelters around the world. Works
    fine.

    Use of the extensions does take a little getting used to. For example, to run
    a task every 5 milliseconds one does not exit and request reactivation in the
    said 5 milliseconds. Instead, request the time when activated and at the end
    of each iteration request reactivation or resumption in 5 milliseconds minus
    however long the current iteration took.

    --
    It's turtles, all the way down.

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

    The Natural Philosopher wrote:
    > Matt Giwer wrote:

    ....
    >> 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.


    I guess I have been confused by the necessity to have the BIOS reflect new
    hardware before linux notices it is there.

    --
    As pf July 2007, the Iraq war is costing the same as three nuclear aircraft
    carriers every month. Never again question the cost of a carrier.
    -- The Iron Webmaster, 3841
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  10. Re: All RTOS (linux Based ) Other than RT-Linux

    Matt Giwer wrote:

    > The Natural Philosopher wrote:
    >> Matt Giwer wrote:

    > ...
    >>> 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.

    >
    > I guess I have been confused by the necessity to have the BIOS reflect new
    > hardware before linux notices it is there.
    >


    And right here you made the next error
    --
    Failure is not an option. It comes bundled with your Microsoft product.


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

    Peter Köhlmann wrote:
    > Matt Giwer wrote:
    >> The Natural Philosopher wrote:
    >>> Matt Giwer wrote:

    >> ...
    >>>> 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.

    >> I guess I have been confused by the necessity to have the BIOS reflectnew
    >> hardware before linux notices it is there.


    > And right here you made the next error


    Odd that it is required. Perhaps you could take the time to explain.

    --
    Hodie postridie Nonas Augustas MMVII est
    -- The Ferric Webceasar
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  12. Re: All RTOS (linux Based ) Other than RT-Linux

    Matt Giwer wrote:
    > Peter Köhlmann wrote:
    >> Matt Giwer wrote:
    >>> The Natural Philosopher wrote:
    >>>> Matt Giwer wrote:
    >>> ...
    >>>>> 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.
    >>> I guess I have been confused by the necessity to have the BIOS
    >>> reflect new
    >>> hardware before linux notices it is there.

    >
    >> And right here you made the next error

    >
    > Odd that it is required. Perhaps you could take the time to explain.
    >


    Th BIOS merely provide a set of routines that are hopefully

    - enough to get the machine to boot something else and
    - MAY be used by whatever else runs to access the hardware, but its only
    MAY.

    In fact most OS'es these days simply use the BIOS to bootstrap the boot
    loader, and maybe access the boot disk: Once the OS is loaded it is
    completely bypassed.

    So in reality, all the BIOS dos in most systems is run the disk system
    and select a boot drive, and provide a minimal amount of screen/keyboard
    stuff for boot diagnostics.

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

    The Natural Philosopher writes:
    > In fact most OS'es these days simply use the BIOS to bootstrap the boot
    > loader, and maybe access the boot disk


    Linux itself does not use the BIOS at all. All bootloaders use it, but the
    bootloader is not part of the OS.

    > Once the OS is loaded it is completely bypassed.


    Correct, but there may be hardware that is initialized by the BIOS.
    --
    John Hasler
    john@dhh.gt.org
    Dancing Horse Hill
    Elmwood, WI USA

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

    The Natural Philosopher wrote:
    > Matt Giwer wrote:
    >> Peter Köhlmann wrote:
    >>> Matt Giwer wrote:
    >>>> The Natural Philosopher wrote:
    >>>>> Matt Giwer wrote:
    >>>> ...
    >>>>>> 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 formof
    >>>>> basic keyboard and screen control. In case intervention is needed.
    >>>> I guess I have been confused by the necessity to have the BIOS
    >>>> reflect new
    >>>> hardware before linux notices it is there.
    >>> And right here you made the next error

    >> Odd that it is required. Perhaps you could take the time to explain.


    > Th BIOS merely provide a set of routines that are hopefully


    > - enough to get the machine to boot something else and
    > - MAY be used by whatever else runs to access the hardware, but its only
    > MAY.


    > In fact most OS'es these days simply use the BIOS to bootstrap the boot
    > loader, and maybe access the boot disk: Once the OS is loaded it is
    > completely bypassed.


    > So in reality, all the BIOS dos in most systems is run the disk system
    > and select a boot drive, and provide a minimal amount of screen/keyboard
    > stuff for boot diagnostics.


    What started this was my statement that the keypresses are found by accessing
    BIOS.

    However my experience is that all hardware changes have to be registeredin
    BIOS before they are recognized by the OS, linux or otherwise. I can see how
    once in BIOS the OS knows what to "look" for and then deal with it.

    Not having actually followed the motherboard traces from the keyboard plug to
    see where they lead I cannot swear the BIOS is the only place where an OScan
    get the keypresses. However if the BIOS is not needed what his the physical
    access point the linux uses to get the keypress data?

    --
    Al Qaeda is back to its pre-911 strength of 300. I am so frightened I can
    only laugh to relieve the anxiety. 300 is the highest US government estimate
    of their numbers ever made public.
    -- The Iron Webmaaster, 3831
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    commentary http://www.giwersworld.org/opinion/running.phtml a5


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

    Matt Giwer wrote:

    > Not having actually followed the motherboard traces from the
    > keyboard plug to see where they lead I cannot swear the BIOS is the only
    > place where an OS can get the keypresses. However if the BIOS is not
    > needed what his the physical access point the linux uses to get the
    > keypress data?


    It depends on the physical device. A PS/2 keyboard is connected to
    different hardware, and is served by a different handler, than is e.g. a
    wireless USB keyboard. When the OS installs drivers, for all physical
    devices, the drivers return the logical device type, e.g. display, HD.
    On universal adapters, like SCSI or USB, every connected device can be
    of an different type. The OS will send (or receive) requests to logical
    devices, which are translated by the handler into commands to the
    physical device.

    DoDi

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

    Matt Giwer wrote:
    > The Natural Philosopher wrote:
    >> Matt Giwer wrote:
    >>> Peter Köhlmann wrote:
    >>>> Matt Giwer wrote:
    >>>>> The Natural Philosopher wrote:
    >>>>>> Matt Giwer wrote:
    >>>>> ...
    >>>>>>> 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.
    >>>>> I guess I have been confused by the necessity to have the BIOS
    >>>>> reflect new
    >>>>> hardware before linux notices it is there.
    >>>> And right here you made the next error
    >>> Odd that it is required. Perhaps you could take the time to explain.

    >
    >> Th BIOS merely provide a set of routines that are hopefully

    >
    >> - enough to get the machine to boot something else and
    >> - MAY be used by whatever else runs to access the hardware, but its
    >> only MAY.

    >
    >> In fact most OS'es these days simply use the BIOS to bootstrap the
    >> boot loader, and maybe access the boot disk: Once the OS is loaded it
    >> is completely bypassed.

    >
    >> So in reality, all the BIOS dos in most systems is run the disk system
    >> and select a boot drive, and provide a minimal amount of
    >> screen/keyboard stuff for boot diagnostics.

    >
    > What started this was my statement that the keypresses are found by
    > accessing BIOS.
    >
    > However my experience is that all hardware changes have to be
    > registered in BIOS before they are recognized by the OS, linux or
    > otherwise. I can see how once in BIOS the OS knows what to "look" for
    > and then deal with it.
    >
    > Not having actually followed the motherboard traces from the
    > keyboard plug to see where they lead I cannot swear the BIOS is the only
    > place where an OS can get the keypresses. However if the BIOS is not
    > needed what his the physical access point the linux uses to get the
    > keypress data?
    >


    Interrupt off the hardware controller that services the keyboard.

    The vectors for these are held in RAM. They can be changed. You can
    install your own. Most systems do. IIRC the first thing a bios will do
    on boot is set these vectors up. Until it does the keyboard won;t work.
    As soon as the OS kernel comes in, it will rewrite some or all of them
    to point to its handlers.

    What happens is that - say - a keypress is recogniosed by the keyboard
    peripheral chip. A small computer in its own right, whose job is to wait
    for keypresses and maybe mouse movements and the like. These days its
    probably the generic USB controller, and every time a block of data
    comes in,depending on how its programmed, it will either raise an
    interrupt line on every byte, or when its small internal buffer is full.

    The interrupt lines go into another small piece of hardware - the
    interrupt controller - and that will register which peripheral has
    raised the interrupt, and pass a general interrupt along to the
    processsor, which will stop, shove its program counter in the stack,
    read the interrupt NUMBER from teh interrupt controller, and jump
    immdiately to the contents of teh NUMBERE'th row of a table held in
    (low?) RAM That might at one time have been pointing at BIOS ROM, but
    fter te OS has does its laoding, itr won;t be. It will point to the USB
    interrupt service routine.

    What THAT des is read te USB device directly, and find out something
    about the device that caused the USB port to wake up. Decide its a
    keyboard key press and jump to a specific bit of code that will reda
    that byte of data, put it in a buffer, raise a flag to say 'keyboard
    data available' and then probabably call the scheduling part of the
    multitasker to tell it to resume any threads that are halted pending
    keyboard input. Then it will issue a return from interrupt and teh
    processor will resume what it was doing by popping its program cunter
    from the stack.

    Now the next time the scheduler suspends the thread the processor was
    executing, it will immediately resume whatever task(s) was/were waiting
    for keyboard input. In whatever priority they were listed. Example: Some
    keys are flagged as super keys' and may be examined and acted on by the
    low level daemons..a break key for example will be examined by low level
    software t see if it means it needs to do Something Awful. So every
    process that MIGHT want to know what key is pressed or what button is
    clicked must examine all the inputs, and if they decide its not for
    them, leave it there and go back to sleep. Finally someone - say the
    application focus - gets the keystroke and says 'aha' I must type an A
    on the application..AND REMOVE IT FROM THE BUFFER. At this point its
    gone, No other application will get it, and if there are other lower
    priority task that might be waiting for it, they will either find no
    data, or won't even be woken up. If the keyboard interface is written
    well, it will call the scheduler when the command 'empty the buffer' is
    received and clear all wakeup flags from threads waiting for keyboard input.

    Don;'t hold me to the exact details of this, buts thats broadly how it
    happened the last time I wrote this sort of stuff, which was 20 years
    ago on an 8086...:-)

    The fundamental thing is that a BIOS ONLY has to carry enough code to
    boot the OS. Essentially that means

    - set up a basic screen and keyboard and disk driver kernel
    - read the NVRAM to find out where to boot from, and what type of built
    in driver to use.
    -load and dive into the boot loader
    - bye bye kansas.

    After that the whole machine apart from the BIOS PROMS is available
    for modification, and in most cases, it will be modified completely.

    In general the kernel will rush around interrogating I/O ports to find
    responses it recognises, and setting up handlers for what it finds: In
    case of unknown issues, it will refer to its disk based config files to
    load the correct stuff. Once it is relatively happy, it will launch the
    init daemon, which looks in ITS config files and carries on spawning
    daemons that get the machine up and running, until it finally spawns
    some kind of user interface.

    At that point the BIOS is just a set of ROMS, idle and silent, and
    completely forgotten.

    If for no other reason than the ROM bus speed is often WAY below the RAM
    bus speed: Using the ROMS will slow you down.

    So, The onboard ROM BIOS only needs to understand the boot hardware. Of
    course you COULD talk about the hardware interface systems in the kernel
    as a BIOS as well, and be correct to do so, but BIOS on Intel machines
    of the PC variety is generally held to be that part that comes with the
    hardware in ROM: In a Linux context the terns 'device drivers' or
    'device subsystem' and 'kernel' would be used instead to talk about
    various aspects of the kernel that deal with interfacing with the hardware.

    I hope that helps.








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

    The Natural Philosopher wrote:
    ....
    > I hope that helps.


    Yes, thank you.

    --
    Every paid position as a university professor originated as a labor of love
    without any form of financial reward.
    -- The Iron Webmaster, 3849
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