netdev - Re: [PATCH net] r8169: fix LED-related deadlock on module removal

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Message-ID: <CAFSsGVsYBJdB0-ve_bxFU8Ps-MS69YSadxqPe39X-6ui5ECiWw@mail.gmail.com>
Date: Thu, 18 Apr 2024 16:33:37 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Lukas Wunner <lukas@...ner.de>, Jakub Kicinski <kuba@...nel.org>, 
	"stable@...r.kernel.org" <stable@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] r8169: fix LED-related deadlock on module removal

On Thu, Apr 18, 2024 at 11:55 AM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Thu, Apr 18, 2024 at 12:33:00AM +0200, Lukas Wunner wrote:
> > On Wed, Apr 17, 2024 at 09:43:27AM +0200, Greg KH wrote:
> > > On Wed, Apr 17, 2024 at 09:16:04AM +0200, Heiner Kallweit wrote:
> > > > On 17.04.2024 09:04, Greg KH wrote:
> > > > > On Wed, Apr 17, 2024 at 08:02:31AM +0200, Heiner Kallweit wrote:
> > > > >> On 17.04.2024 04:34, Jakub Kicinski wrote:
> > > > >>> On Mon, 15 Apr 2024 13:57:17 +0200 Heiner Kallweit wrote:
> > > > >>>> Binding devm_led_classdev_register() to the netdev is problematic
> > > > >>>> because on module removal we get a RTNL-related deadlock. Fix this
> > > > >>>> by avoiding the device-managed LED functions.
> > > > >>>>
> > > > >>>> Note: We can safely call led_classdev_unregister() for a LED even
> > > > >>>> if registering it failed, because led_classdev_unregister() detects
> > > > >>>> this and is a no-op in this case.
> > > > >>>>
> > > > >>>> Fixes: 18764b883e15 ("r8169: add support for LED's on RTL8168/RTL8101")
> > > > >>>> Cc: <stable@...r.kernel.org> # 6.8.x
> > > > >>>> Reported-by: Lukas Wunner <lukas@...ner.de>
> > > > >>>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
> > > > >>
> > > > >> This is a version of the fix modified to apply on 6.8.
> > > > >
> > > > > That was not obvious at all :(
> > > > >
> > > > Stating "Cc: <stable@...r.kernel.org> # 6.8.x" isn't sufficient?
> > >
> > > Without showing what commit id this is in Linus's tree, no.
> >
> > The upstream commit id *is* called out in the patch, but it's buried
> > below the three dashes:
> >
> >     The original change was introduced with 6.8, 6.9 added support for
> >     LEDs on RTL8125. Therefore the first version of the fix applied on
> >     6.9-rc only. This is the modified version for 6.8.
> >     Upstream commit: 19fa4f2a85d7
> >                      ^^^^^^^^^^^^
> >
> > The proper way to do this is to prominently add ...
> >
> >     commit 19fa4f2a85d777a8052e869c1b892a2f7556569d upstream.
> >
> > ... or ...
> >
> >     [ Upstream commit 19fa4f2a85d777a8052e869c1b892a2f7556569d ]
> >
> > ... as the first line of the commit message, as per
> > Documentation/process/stable-kernel-rules.rst
> >
>
> Yes, Heiner, please resubmit this, AND submit the fix-for-this-fix as
> well, so that if we take this patch, it is not broken.
>
OK. The fix-for-the-fix was included already. It's trivial and IMO submitting it
separately would just create overhead.

> thanks,
>
> greg k-hj