linux-kernel - Re: [PATCH] libkmod-module: Remove directory existence check for KMOD_MODULE

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Date:	Thu, 19 Feb 2015 09:10:12 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Lucas De Marchi <lucas.de.marchi@...il.com>
Cc:	Harish Jenny K N <harish_kandiga@...tor.com>,
	linux-modules <linux-modules@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"greg KH" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] libkmod-module: Remove directory existence check for KMOD_MODULE_BUILTIN

Lucas De Marchi <lucas.de.marchi@...il.com> writes:
> On Wed, Feb 18, 2015 at 2:07 AM, Rusty Russell <rusty@...tcorp.com.au> wrote:
> Yeah, I just thought (an wanted that) the attributes were being
> created first and then hooked up in the sysfs tree under
> /sys/module/<modulename>. I.e. if the directory exists and there's no
> initstate this is because it's a builtin module. I don't want to
> wait/sleep on the file to appear because users of
> kmod_module_get_initstate() may not tolerate this behavior.
>
> Looking up at the old module-init-tools, it used an ugly loop with
> usleep() before trying to read the file again :-/
>
> Can we change kernel side guaranteeing the initstate file appears
> together with the directory?

Greg?  The core problem is that kmod looks for
/sys/module/<name>/initstate; if it's not there, it assumes a builtin
module.

However, this is racy when a module is being inserted.  Is there a way
to create this sysfs file and dir atomically?

Thanks,
Rusty.
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