Re: Documentation / code sample wanted.

[Jody Pearson <jody.pearson@cern.ch>]

Hi Dick, All,

>
>This has become a FAQ, probably because people
>don't know what a kernel is. They think it's
>just some 'C' code in which you can do anything
>the 'C' compiler lets you do.
>  
>
In this case, I was being stupid with the gethostbyname exmaple. But I 
do know what a kernel is !

To fill in the blanks, I am writing a network based filesystem, and I 
now realise that the place to do the gethostbyname() is in a mount helper.

>Important! The kernel is not a 'task' it doesn't
>have a context. Everything it has been designed
>to do, is to perform systematic tasks upon behalf
>of the caller, calling from user-mode context.
>When it is executing, it is executing upon behalf
>of a user-mode task. It is doing what the user-mode
>task doesn't know how, or isn't trusted, to do.
>
What I would like to achive is a self-contained module which implements 
a filesystem. The user-space apps then interact with the fs as normal.

I am trying to avoid havng "helper daemons" for various reasons, too 
long to go into here

>
>The only thing that can call the kernel and
>successfully accomplish what it intended to do, is
>a user-mode task. Therefore, if you want to call
>the kernel, you do it from a user-mode program.
>It's just that simple.
>
And if your a filesystem ? Is it really recommended to do;

userspace->kernel->userspace->kernel->userspace ? That seems like a lot 
of context switching to me.

>
>You do this, by creating a user-mode daemon that
>sleeps in select() or poll() until the kernel code
>wakes it, 
>
[snip]

As I said, for my own reasons I would like not to have a deamon like this.

Thanks for the help.

Jody

-- 
Chaos, Panic, Pandemonium...  my work here is done.