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From:   Maxim Kiselev <bigunclemax@gmail.com>
Date:   Wed, 14 Dec 2022 14:42:29 +0300
Message-ID: <CALHCpMgL-GQQQYMRii8PUkXVw_4Hit7MAUF+DsvAaT6eFPhtsQ@mail.gmail.com>
Subject: Re: Subject: Locking mv88e6xxx_reg_lock twice leads deadlock for
 88E6176 switch
To:     Vladimir Oltean <olteanv@gmail.com>
Cc:     fido_max@inbox.ru, mw@semihalf.com, Andrew Lunn <andrew@lunn.ch>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Richard Cochran <richardcochran@gmail.com>,
        Russell King <linux@armlinux.org.uk>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
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Thanks for the quick fix, Vladimir!

=D1=81=D1=80, 14 =D0=B4=D0=B5=D0=BA. 2022 =D0=B3. =D0=B2 14:04, Vladimir Ol=
tean <olteanv@gmail.com>:
>
> On Wed, Dec 14, 2022 at 01:58:55AM +0300, Maksim Kiselev wrote:
> > Hello, friends.
>
> Hello.
>
> > I have a device with Marvell 88E6176 switch.
> > After 'mv88e6xxx: fix speed setting for CPU/DSA ports (cc1049ccee20)'co=
mmit was applied to
> > mainline kernel I faced with a problem that switch driver stuck at 'mv8=
8e6xxx_probe' function.
>
> Sorry for that.
>
> > I made some investigations and found that 'mv88e6xxx_reg_lock' called t=
wice from the same thread which leads to deadlock.
> >
> > I added logs to 'mv88e6xxx_reg_lock' and 'mv88e6xxx_reg_unlock' functio=
ns to see what happened.
>
> I hope you didn't spend too much time doing that. If you enable CONFIG_PR=
OVE_LOCKING,
> you should automatically get a stack trace with the two threads that
> acquired the mutex leading to the deadlock.
>
> I've sent a patch which solves that issue here:
> https://patchwork.kernel.org/project/netdevbpf/patch/20221214110120.33684=
72-1-vladimir.oltean@nxp.com/
> I've regression-tested it on 88E6390. Please confirm with a Tested-by:
> tag on that patch that it does resolve the deadlock for 88E6176.
>
> Thanks for reporting!