linux-kernel - Re: [RFC] firmware loader: retry _nowait requests when userhelper is not yet available

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Date:	Fri, 16 Mar 2012 17:33:45 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Christian Lamparter <chunkeey@...glemail.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
	alan@...rguk.ukuu.org.uk,
	Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: [RFC] firmware loader: retry _nowait requests when userhelper is
 not yet available

On Fri, Mar 16, 2012 at 5:23 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>
> OK, but that asynchronous thread needs to know whether or not the system is up.

Sure.

> It can use the usermodehelper_is_disabled() check, but that needs to be done
> under read_lock_usermodehelper() and it can't release the lock before
> calling _request_firmware(), or all that thing would be racy.

Well, I think that it would actually be a good idea to perhaps split
up that existing _request_firmware() a bit. In fact, it might be good
to split up that whole "fw_create_instance()" too - and re-organize
the code a bit so that you end up creating the "firmware_priv" thing
first.

So maybe we could have a helper function that does that first part of
fw_create_instance() (the part that allocates it and does the
__module_get() part and other really basic initialization), and that
can be called unconditionally by the request_firmware_nowait() code
early.

That early part probably should *not* create the device attribute
files etc (although who knows - maybe sysfs is ok at this point).

So I think we really could re-organize the code to do a sane job - and
move just the actual udev setup etc to the final part that needs to be
delayed.

Hmm?

I haven't looked very deeply into it, but my *gut* feel is that it
should be doable pretty cleanly.

But yeah, it would be more than a little one-liner. I think it might
be worth it, though. Clearly separating out the three stages: "setup"
-> "wait for system to be ready" -> "do the actual load".

Then, the regular request_firmware() function would do exactly the
same things, except it would never do the "wait for system to be
ready" part: it would just fail with the warning if it wasn't already
ready. So they'd still share all the basic core code, it would just be
a slightly different organization from what it is now.

                 Linus
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