[KJ] Need to get some very basic things sorted out

[KJ] Need to get some very basic things sorted out

[Dinolinux]

Hey!

If you noted my last message and thougt that it was very noob, don't
count on any more advancement here. ;-)

The thing is that I need help to get started. I'm in the process of
learning C and I need to know how the kernel patching and distribution
works.

1 - I've looked into the kernel-janitor TODO list and I don't exactly
understand lines like this:
/Audit return codes (and handle failure correctly) for: /(What does
this mean???)/
- request_region() /(This one was tricky)/
/Where do I have to look for the code? Do I have to go to the _entire_
kernel tree?

2 - How do I start writing patches? This doesn't tell me much:
/Before attacking any of these, we suggest sending a few patches in
advance to see if you are doing something wrong, or if someone else
is already doing same work.
Read related threads in the mailing list archive.
/Which patches? Where do I find a TODO list of patches that need to be
done? The lkml mailing list don't say me much.

I hope this wasn't _too_ noob :-)

    Dinolinux


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Re: [KJ] Need to get some very basic things sorted out

[lounprime]

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Gentle People,
 
I'm newly registered member to the list and wanted to ask a question,
if someone has time.
 
Is anyone aware of any outstanding bug reports regarding Slab Corruption
in slab.c?
 
My most sincere thanks for your time,
 
LouNprime@aol.com
Lou Bangert
 
/Lou:-) 
 
-----Original Message-----
From: Dinolinux <slackfan@users.sourceforge.net>
To: kernel-janitors@lists.osdl.org
Sent: Wed, 28 Sep 2005 17:14:22 +0200
Subject: [KJ] Need to get some very basic things sorted out


Hey!

If you noted my last message and thougt that it was very noob, don't
count on any more advancement here. ;-)

The thing is that I need help to get started. I'm in the process of
learning C and I need to know how the kernel patching and distribution
works.

1 - I've looked into the kernel-janitor TODO list and I don't exactly
understand lines like this:
/Audit return codes (and handle failure correctly) for: /(What does
this mean???)/
- request_region() /(This one was tricky)/
/Where do I have to look for the code? Do I have to go to the _entire_
kernel tree?

2 - How do I start writing patches? This doesn't tell me much:
/Before attacking any of these, we suggest sending a few patches in
advance to see if you are doing something wrong, or if someone else
is already doing same work.
Read related threads in the mailing list archive.
/Which patches? Where do I find a TODO list of patches that need to be
done? The lkml mailing list don't say me much.

I hope this wasn't _too_ noob :-)

    Dinolinux


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Re: [KJ] Need to get some very basic things sorted out

[Alexey Dobriyan]

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On Wed, Sep 28, 2005 at 05:14:22PM +0200, Dinolinux wrote:
> The thing is that I need help to get started. I'm in the process of
> learning C and I need to know how the kernel patching and distribution
> works.
> 
> 1 - I've looked into the kernel-janitor TODO list and I don't exactly
> understand lines like this:
> /Audit return codes (and handle failure correctly) for: /(What does
> this mean???)/

Consider example:

	buf = kmalloc(256, GFP_KERNEL);
	buf[0] = 'L';

See the prolem? kmalloc() can return NULL, which means "Not enough
memory". This buggy code doesn't check for NULL.

	buf = kmalloc(256, GFP_KERNEL);
	if (!buf)
		return -ENOMEM;
	buf[0] = 'L';

This sane code checks return value of kmalloc() and propagate proper
error. Note, note, note: undoing all previous allocations if one fails
is mandatory. See code around existing kmalloc()s to see how it's
usually done.

> - request_region() /(This one was tricky)/
> /Where do I have to look for the code?

grep for request_region. -C option of grep is very handy in such cases.

> Do I have to go to the _entire_ kernel tree?

It would be nice if each and every request_region() call is checked for
return value. Much patience is required for this.

> 2 - How do I start writing patches?

less Documentation/SubmittingPatches	(section 1 and the rest of
course)

> This doesn't tell me much:
> /Before attacking any of these, we suggest sending a few patches in
> advance to see if you are doing something wrong, or if someone else
> is already doing same work.
> Read related threads in the mailing list archive.
> /Which patches? Where do I find a TODO list of patches that need to be
> done?

You're reading one of them -- kernel-janitors TODO list. Things to be
done.


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Re: [KJ] Need to get some very basic things sorted out

[Randy.Dunlap]

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On Wed, 28 Sep 2005, Alexey Dobriyan wrote:

> On Wed, Sep 28, 2005 at 05:14:22PM +0200, Dinolinux wrote:
> > The thing is that I need help to get started. I'm in the process of
> > learning C and I need to know how the kernel patching and distribution
> > works.
> >
> > 1 - I've looked into the kernel-janitor TODO list and I don't exactly
> > understand lines like this:
> > /Audit return codes (and handle failure correctly) for: /(What does
> > this mean???)/
>
> Consider example:
>
> 	buf = kmalloc(256, GFP_KERNEL);
> 	buf[0] = 'L';
>
> See the prolem? kmalloc() can return NULL, which means "Not enough
> memory". This buggy code doesn't check for NULL.
>
> 	buf = kmalloc(256, GFP_KERNEL);
> 	if (!buf)
> 		return -ENOMEM;
> 	buf[0] = 'L';
>
> This sane code checks return value of kmalloc() and propagate proper
> error. Note, note, note: undoing all previous allocations if one fails
> is mandatory. See code around existing kmalloc()s to see how it's
> usually done.
>
> > - request_region() /(This one was tricky)/
> > /Where do I have to look for the code?
>
> grep for request_region. -C option of grep is very handy in such cases.
>
> > Do I have to go to the _entire_ kernel tree?
>
> It would be nice if each and every request_region() call is checked for
> return value. Much patience is required for this.


Jeff Garzik did a good piece of that work a few days ago.
His email also tells what pieces remain to be done.

See
  http://marc.theaimsgroup.com/?l=linux-kernel&m=112742405517833&w=2

-- 
~Randy

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Re: [KJ] Need to get some very basic things sorted out

[Ricardo Nabinger Sanchez]

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Quoting  Alexey Dobriyan <adobriyan@gmail.com>
Sent on  Wed, 28 Sep 2005 21:56:14 +0400

Hello,

> 	buf = kmalloc(256, GFP_KERNEL);
> 	if (!buf)
> 		return -ENOMEM;
> 	buf[0] = 'L';

*please* correct me if I'm wrong, but I remember reading somewhere a Linus'
message stating that one should not use "if (!pointer)" for pointers when
it is intended to do "if (pointer == NULL)".  in short, what I remember is
that one should not assume that NULL == 0, thus the explicit NULL checking.

a quick search revealed these:

	http://lwn.net/Articles/93574/
	http://lwn.net/Articles/93577/

are these still valid?  (I presume yes, but...)

Regards.

-- 
Ricardo Nabinger Sanchez
GNU/Linux #140696 [http://counter.li.org]
Slackware Linux + FreeBSD

  Left to themselves, things tend to go from bad to worse.

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Re: [KJ] Need to get some very basic things sorted out

[Randy.Dunlap]

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On Wed, 28 Sep 2005, Ricardo Nabinger Sanchez wrote:

> Quoting  Alexey Dobriyan <adobriyan@gmail.com>
> Sent on  Wed, 28 Sep 2005 21:56:14 +0400
>
> Hello,
>
> > 	buf = kmalloc(256, GFP_KERNEL);
> > 	if (!buf)
> > 		return -ENOMEM;
> > 	buf[0] = 'L';
>
> *please* correct me if I'm wrong, but I remember reading somewhere a Linus'
> message stating that one should not use "if (!pointer)" for pointers when
> it is intended to do "if (pointer == NULL)".  in short, what I remember is
> that one should not assume that NULL == 0, thus the explicit NULL checking.
>
> a quick search revealed these:
>
> 	http://lwn.net/Articles/93574/
> 	http://lwn.net/Articles/93577/

These say:
	don't use 0 for a (null) pointer and
	don't use NULL for an integer value.

> are these still valid?  (I presume yes, but...)

Sure, those are valid, but they aren't the same as the
first example above.  I don't see anything wrong with what
Alexey wrote.

-- 
~Randy

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