linux-kernel - Re: [PATCH] backports: backport drvdata = NULL core driver fixes

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Message-ID: <CAB=NE6WfbauZnzCT=jgfUtc2Roe7WfY=G7Z5OAobc9YLc0nCvw@mail.gmail.com>
Date:	Fri, 19 Jul 2013 14:41:37 -0700
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	"backports@...r.kernel.org" <backports@...r.kernel.org>,
	Hans de Goede <hdegoede@...hat.com>,
	USB list <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jslaby@...e.cz>, Jiri Kosina <jkosina@...e.cz>,
	Felix Fietkau <nbd@...nwrt.org>
Subject: Re: [PATCH] backports: backport drvdata = NULL core driver fixes

On Fri, Jul 19, 2013 at 2:27 PM, Julia Lawall <julia.lawall@...6.fr> wrote:
> On Fri, 19 Jul 2013, Luis R. Rodriguez wrote:
>
>> On Fri, Jul 19, 2013 at 2:07 PM, Luis R. Rodriguez
>> <mcgrof@...not-panic.com> wrote:
>> >> This is not a very good idea.  Although setting drvdata to NULL allowed
>> >> a lot of code to be removed, it also exposed a bunch of hidden bugs --
>> >> drivers were using the drvdata value even after their remove function
>> >> returned.
>> >
>> > Eek, have we not SmPL'ify'd a proof yet to ensure code like this no
>> > longer exists? Julia? :)
>>
>> Come to think of it, perhaps we should require *proof* with SmPL like
>> this in future to avoid regressions ?
>
> Is it a concurrency problem?  SmPL is not so good at that in the general
> case.  One would have to know a specific case where other functions of the
> driver can be invoked after remove.

Thanks Julia. In that case I'm going to just leave this in place given
that if there's a bug upstream we'll get it fixed as soon as a
respective patch gets upstream as well. That is, we are not using old
drivers, we use the same upstream drivers so if a regression was found
in backports the fix must go upstream s well. This is one of the
benefits of backporting -- the range of users and testers increases
and we still benefit from the upstream bandwagon.

  Luis
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