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Date: Wed, 15 Jan 2025 06:18:20 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: <andrew+netdev@lunn.ch>, <davem@davemloft.net>, <edumazet@google.com>,
 <horms@kernel.org>, <jdamato@fastly.com>, <netdev@vger.kernel.org>,
 <pabeni@redhat.com>
Subject: Re: [PATCH net-next v2 02/11] net: make netdev_lock() protect
 netdev->reg_state
Message-ID: <20250115061820.4d6d03a9@kernel.org>
In-Reply-To: <20250115083023.31347-1-kuniyu@amazon.com>
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	<20250115083023.31347-1-kuniyu@amazon.com>
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On Wed, 15 Jan 2025 17:30:23 +0900 Kuniyuki Iwashima wrote:
> > @@ -10668,7 +10668,9 @@ int register_netdevice(struct net_device *dev)
> >  
> >  	ret = netdev_register_kobject(dev);
> >  
> > +	netdev_lock(dev);
> >  	WRITE_ONCE(dev->reg_state, ret ? NETREG_UNREGISTERED : NETREG_REGISTERED);
> > +	netdev_unlock(dev);  
> 
> Do we need the lock before list_netdevice() ?

Fair point, we don't. I couldn't decide whether it's more logical 
to skip the locking since device is not listed, or lock it, just
because we say that @reg_state is supposed to be write protected.