linux-kernel - Re: Tips for module

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Date:	Thu, 15 Oct 2009 11:58:19 -0400
From:	Gregory Haskins <gregory.haskins@...il.com>
To:	Daniel Walker <dwalker@...o99.com>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Tips for module_init() dependencies

Daniel Walker wrote:
> On Thu, 2009-10-15 at 09:01 -0400, Gregory Haskins wrote:
> 
>> may break, because the kernel seems to have no concept of
>> interdependency between foo_init() and bar_init(), and therefore
>> bar_init() may call foo() before foo_init() has executed.
>>
>> There are various ways to solve this problem, such as deferring calling
>> foo() with a workqueue or something, but I was wondering if there was a
>> better/standard way to do this that I am missing?
>>
>> The problem I am having specifically is that I am trying to call
>> configfs_register_subsystem() in a module_init(), but this breaks when
>> built into the kernel based on sheer bad luck that configfs gets
>> initialized after me.  To date I have worked around this by forcing my
>> code to only support built-in, and using late_initcall() instead or
>> module_init.  This works, but it only means I am putting the problem off
>> (code that depends on *me* has to use similar tricks, etc.
> 
> You can't modify the build order so your module get "builtin" after
> configfs?
> 

Hi Daniel,

Possibly.

A) Any suggestions on how? Can I express this in Kconfig or something
(i.e. "depends on FOO").  I currently have "select FOO" in the BAR
object, but this doesn't seem to be sufficient to describe the relationship.

B) Do I have to make the entire chain follow suit? (I have C deps on B,
B deps on A kind of scenarios)

Kind Regards,
-Greg



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