linux-kernel - Re: [RFC PATCH 08/13] driver core: firmware loader: fix device lifetime

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Message-ID: <20120726174617.GA9161@aftab.osrc.amd.com>
Date:	Thu, 26 Jul 2012 19:46:17 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 08/13] driver core: firmware loader: fix device
 lifetime

On Thu, Jul 26, 2012 at 11:44:48PM +0800, Ming Lei wrote:
> On Thu, Jul 26, 2012 at 8:20 PM, Borislav Petkov <bp@...64.org> wrote:
> >
> > Ok, here's what I got from looking at the patch:
> >
> > Your commit message says: "Also request_firmware_nowait should be called
> > in atomic context now, so fix the obsolete comments."
> >
> > Atomic context in my book means you're not allowed to sleep at all.
> 
> In fact, I mean the function can be called in atomic context now, and
> I know some time ago the function will create kthread to execute
> the request_firmware, and atomic context is not allowed.

Right, but when called with GFP_KERNEL mask, it can sleep, right?

> > But the comment says that it is possible to sleep a little. This is very
> > wrongly formulated AFAICT.
> 
> The function can be run in both contexts, and I don't see any words which
> says the function will sleep.

"
...
 *	Asynchronous variant of request_firmware() for user contexts where
 *	it is not possible to sleep for long time.
 **/
"

Not possible to sleep for a long time means the function still *can*
sleep... even for short time. For a certain definion of "short."

> > But, since request_firmware_nowait receives a GFP mask as one of its
> > arguments and some of its callers don't supply GFP_ATOMIC then this
> > has nothing to do with atomic contexts at all. Then, you should simply
> > explain in the comment why exactly callers aren't allowed to be sleeping
> > for a long time. And using adjectives like "long" or "short" is very
> > misleading in such explanations so please be more specific as to why the
> 
> It is the original one, and I don't think it is wrong. Also it
> shouldn't be covered
> by this patch.
> 
> Maybe I shouldn't have fixed the comment in this patch.

Why, simply fix the comment to adhere to what the function does. And
since it can sleep, maybe the easiest fix is to say simply that:
"function can sleep", right?

-- 
Regards/Gruss,
Boris.

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