linux-kernel - Re: Tips for module

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Date:	Thu, 15 Oct 2009 12:13:30 -0400
From:	Gregory Haskins <gregory.haskins@...il.com>
To:	Randy Dunlap <rdunlap@...otime.net>
CC:	Daniel Walker <dwalker@...o99.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Tips for module_init() dependencies

Randy Dunlap wrote:
> On Thu, 15 Oct 2009 11:58:19 -0400 Gregory Haskins wrote:
> 
>> 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.
> 
> Not in Kconfig, only in Makefile(s).
> and please put #comments in them explaining the ordering requirements/needs.

Hi Randy,

Something like this?

----------

# cat drivers/bar/Makefile

bar.o: foo.o
obj-$CONFIG_BAR += bar.o

----------

?

Kind Regards,
-Greg


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