linux-kernel - Re: patch problem - mv88e6xxx: flush switchdev FDB workqueue

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Date:   Mon, 14 Mar 2022 11:17:50 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     Daniel Suchy <danny@...ysek.cz>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "rafael.richter@....de" <rafael.richter@....de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: patch problem - mv88e6xxx: flush switchdev FDB workqueue

On Mon, Mar 14, 2022 at 08:21:30AM +0100, gregkh@...uxfoundation.org wrote:
> On Mon, Mar 14, 2022 at 07:38:50AM +0100, gregkh@...uxfoundation.org wrote:
> > On Sun, Mar 13, 2022 at 02:10:31PM +0000, Vladimir Oltean wrote:
> > > Hi Daniel,
> > > 
> > > On Sun, Mar 13, 2022 at 03:03:07PM +0100, Daniel Suchy wrote:
> > > > Hello,
> > > > 
> > > > I noticed boot problems on my Turris Omnia (with Marvell 88E6176 switch
> > > > chip) after "net: dsa: mv88e6xxx: flush switchdev FDB workqueue before
> > > > removing VLAN" commit https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=2566a89b9e163b2fcd104d6005e0149f197b8a48
> > > > 
> > > > Within logs I catched hung kernel tasks (see below), at least first is
> > > > related to DSA subsystem.
> > > > 
> > > > When I revert this patch, everything works as expected and without any
> > > > issues.
> > > > 
> > > > In my setup, I have few vlans on affected switch (i'm using ifupdown2 v3.0
> > > > with iproute2 5.16 for configuration).
> > > > 
> > > > It seems your this patch introduces some new problem (at least for 5.15
> > > > kernels). I suggest revert this patch.
> > > > 
> > > > - Daniel
> > > 
> > > Oh wow, I'm terribly sorry. Yes, this patch shouldn't have been
> > > backported to kernel 5.15 and below, but I guess I missed the
> > > backport notification email and forgot to tell Greg about this.
> > > Patch "net: dsa: mv88e6xxx: flush switchdev FDB workqueue before
> > > removing VLAN" needs to be immediately reverted from these trees.
> > > 
> > > Greg, to avoid this from happening in the future, would something like
> > > this work? Is this parsed in some way?
> > > 
> > > Depends-on: 0faf890fc519 ("net: dsa: drop rtnl_lock from dsa_slave_switchdev_event_work") # which first appeared in v5.16
> > 
> > The "Fixes:" tag will solve this, please just use that in the future.
> 
> Ah, you did have a fixes tag here, so then use the way to say "you also
> need to add another patch here" by adding the sha to the line for the
> stable tree:
> 	cc: stable@...r.kernel.org # 0faf890fc519
> 
> So, should I just backport that commit instead?  The "Fixes:" line says
> this needs to be backported to 4.14, which is why I added it to these
> trees.
> 
> thanks,

No, don't backport the dependency, just revert the patch (hence my
question: how can I describe "don't backport beyond commit X"?).

Here, you can apply the revert attached.

View attachment "0001-Revert-net-dsa-mv88e6xxx-flush-switchdev-FDB-workque.patch" of type "text/x-diff" (3851 bytes)