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Date: Tue, 3 Mar 2026 21:21:45 +0100
From: Andrew Lunn <andrew@lunn.ch>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Jens Emil Schulz =?iso-8859-1?Q?=D8stergaard?= <jensemil.schulzostergaard@microchip.com>,
	UNGLinuxDriver@microchip.com,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Simon Horman <horms@kernel.org>, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Woojung Huh <woojung.huh@microchip.com>,
	Russell King <linux@armlinux.org.uk>,
	Steen Hegelund <Steen.Hegelund@microchip.com>,
	Daniel Machon <daniel.machon@microchip.com>,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	devicetree@vger.kernel.org
Subject: Re: [PATCH net-next 8/8] net: dsa: lan9645x: add port statistics
Message-ID: <c327cdb9-ce0c-41dd-917a-429b2b52bc26@lunn.ch>
References: <20260303-dsa_lan9645x_switch_driver_base-v1-0-bff8ca1396f5@microchip.com>
 <20260303-dsa_lan9645x_switch_driver_base-v1-0-bff8ca1396f5@microchip.com>
 <20260303-dsa_lan9645x_switch_driver_base-v1-8-bff8ca1396f5@microchip.com>
 <20260303-dsa_lan9645x_switch_driver_base-v1-8-bff8ca1396f5@microchip.com>
 <20260303160159.efjtqzpa2w4awxht@skbuf>
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In-Reply-To: <20260303160159.efjtqzpa2w4awxht@skbuf>

> > +void lan9645x_stats_get_stats64(struct lan9645x *lan9645x, int port,
> > +				struct rtnl_link_stats64 *stats)
> > +{
> > +	u64 *port_cnt;
> > +
> > +	/* Avoid stats update, as this is called very often by DSA. */
> > +	mutex_lock(&lan9645x->stats->hw_lock);
> 
> This is atomic context, you can't acquire a mutex which may be held by a
> process which sleeps, which also puts you to sleep for it.

Which suggests no testing has been done with kernel configuration
options enabled which does checks for this, deadlock detection, etc.

I would suggest PROVE_LOCKING, DEBUG_SPINLOCK, DEBUG_MUTEXES,
DEBUG_ATOMIC_SLEEP.

	Andrew