linux-kernel - Re: Tips for module

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Date:	Thu, 15 Oct 2009 09:06:45 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Gregory Haskins <gregory.haskins@...il.com>
Cc:	Daniel Walker <dwalker@...o99.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Tips for module_init() dependencies

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.

> 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


---
~Randy
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