Linked lists for userspace programs in Linux

[Chandrasekaran Sivakumar]

Hi,
Apologies from me. I didn't explain my problem properly. I am working on
modifying the linux kernel's scheduler framework to include support for
real-time algorithms. In order to give user inputs such as number of tasks,
their execution cost, period, deadline etc, I am creating an userspace
program. Then this program would transfer control to the kernel to perform
system calls for creation and execution of tasks. Thats why I had to
recompile the kernel. I had planned to use linked list to contain the
multiple execution cost values in each task (for a mixed criticality task
system). As the control is transferred to the kernel, the linked list
should be accessed from the kernel side also. As you had suggested, I had
written my own implementation of linked lists. Please advise me on how to
make this implementation (contained in a header file) common to both kernel
and userspace ? Thank you for your time.

Regards,
chandru


On Mon, Jun 16, 2014 at 11:24 AM, <Valdis.Kletnieks at vt.edu> wrote:

> On Sat, 14 Jun 2014 02:38:19 +0800, Chandrasekaran Sivakumar said:
>
> > I wanted to use linked lists in one of my userspace programs in Linux.
>
> Userspace.  Remember that word.
>
> > 1. I used the modified version of list implementation given in
> > http://isis.poly.edu/kulesh/stuff/src/klist/list.h for my userspace
> > program. But when I compiled the kernel, there were errors showing
> > 'redefinition of struct', 'conflicting types' etc.
>
> You're recompiling the kernel for what reason?  You seem to be confused
> regarding kernel space versus userspace programming...
>
> > 2. When I tried to use list.h as such without any modifications, linked
> > list functions in my userspace program were not identified by the
> compiler
> > and displayed as undefined.
>
> This sounds like you need an introductory C class.
> Did you remember to #include them?
>
> Oh, by the way, keep in mind that the Linux kernel "linked list"
> is actually a circularly linked list - as a result, treating it as a
> normal linked list (particularly when checking for empty list or
> end-of-list)
> is likely to result in hilarity and hijinks for all...
>
> > Would it be okay to modify the variable/function names in a copy of
> list.h
> > and use it in the userspace program ?
>
> You'd probably be better off learning basic data structures well enough
> to write your own implementation.
>
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