netdev - Re: [PATCH net-next 2/8] net: designate XSK pool pointers in queues as "ops protected"

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Message-ID: <20250408075908.27f834da@kernel.org>
Date: Tue, 8 Apr 2025 07:59:08 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Joe Damato <jdamato@...tly.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
 pabeni@...hat.com, andrew+netdev@...n.ch, horms@...nel.org,
 sdf@...ichev.me, hramamurthy@...gle.com, kuniyu@...zon.com
Subject: Re: [PATCH net-next 2/8] net: designate XSK pool pointers in queues
 as "ops protected"

On Mon, 7 Apr 2025 19:17:36 -0700 Joe Damato wrote:
> > -	xp_clear_dev(pool);
> > +	if (netdev) {
> > +		netdev_lock_ops(netdev);
> > +		xp_clear_dev(pool);
> > +		netdev_unlock_ops(netdev);
> > +	}
> >  	rtnl_unlock();  
> 
> Is it actually possible for netdev to be NULL here?

So I've been told in v1 review :) I should have probably linked to
previous postings, these patches had been a part of various series
before.

The code is indeed buggy, tho, we need to move the netdev = pool->netdev
assignment under rtnl_lock..

> I feel like it probably isn't, but if it were possible we'd need an
> else case here to xp_clear_dev(pool) without the netdev_lock_ops?

It does nothing when netdev is null. Actually, due to "other changes"
all callers of xp_clear_dev() are now wrapped in the lock. We can
move the locking inside that helper.