linux-kernel - Re: [PATCH 1/4] module: implement module_inhibit

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Message-ID: <46F86727.4050004@gmail.com>
Date:	Tue, 25 Sep 2007 10:40:55 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
CC:	Jonathan Corbet <corbet@....net>, ebiederm@...ssion.com,
	cornelia.huck@...ibm.com, greg@...ah.com,
	stern@...land.harvard.edu, kay.sievers@...y.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] module: implement module_inhibit_unload()

Rusty Russell wrote:
> On Tue, 2007-09-25 at 08:18 +0900, Tejun Heo wrote:
>>> Given your description of this tool as a "sledgehammer," might it not be
>>> easier to just take and hold module_mutex for the duration of the unload
>>> block?
>> That would be easier but...
>>
>> * It would serialize users of the sledgehammer.
>> * It would block loading modules (which is often more important than
>> unloading them) when things go south.
> 
> My concern is that you're dropping the module mutex around ->exit now.
> I don't *think* this should matter, but it's worth considering.

We always did that.  Before the patch the code segment looked like the
following.

	/* Final destruction now noone is using it. */
	if (mod->exit != NULL) {
		mutex_unlock(&module_mutex);
		mod->exit();
		mutex_lock(&module_mutex);
	}	

> I really wonder if an explicit "kill_this_attribute()" is a better way
> to go than this...

I think this sort of temporary unload blocking would be useful for other
cases like this.

Thanks.

-- 
tejun
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