linux-kernel - Re: [PATCH 1/4] firmware: Refactoring for splitting user-mode helper code

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Date:	Wed, 30 Jan 2013 11:31:00 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Ming Lei <ming.lei@...onical.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] firmware: Refactoring for splitting user-mode helper code

At Wed, 30 Jan 2013 18:25:20 +0800,
Ming Lei wrote:
> 
> On Wed, Jan 30, 2013 at 3:17 PM, Takashi Iwai <tiwai@...e.de> wrote:
> >> The above usermodehelper_read_lock thing may be a functional change,
> >> and looks not what you claimed in commit log, :-). The lock is currently held in
> >> direct loading case, but your patch change the rule. Without holding the lock,
> >> request_firmware() may touch filesystem / storage too early during
> >> kernel boot or system resume in direct loading case.
> >
> > Does it really happen in a real scenario?
> 
> Some crazy drivers might call request_firmware inside resume callback,
> with usermodehelper_read_lock, we can find the mistake easily and log it.

But it's supposed to be cached, no?

> > If so, using usermode helper lock for that purpose sounds like an
> > abuse to be fixed differently or replaced with a better one.
> 
> Might be, but looks not good to introduce this change in a code
> refactoring patch. Or you can do it in another patch for discussion
> if you have better way to handle the situation.

Yes, I already modified the code again.
Will resubmit them soon.


Takashi
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