netdev - Re: patch problem - mv88e6xxx: flush switchdev FDB workqueue

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Date:   Sun, 13 Mar 2022 14:10:31 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Daniel Suchy <danny@...ysek.cz>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "rafael.richter@....de" <rafael.richter@....de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "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

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