netdev - Re: [PATCH net 6/8] ice: improve updating ice_{t, r}x_ring::xsk

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Message-ID: <20240725063858.65803c85@kernel.org>
Date: Thu, 25 Jul 2024 06:38:58 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>, <davem@...emloft.net>,
 <pabeni@...hat.com>, <edumazet@...gle.com>, <netdev@...r.kernel.org>,
 <magnus.karlsson@...el.com>, <aleksander.lobakin@...el.com>,
 <ast@...nel.org>, <daniel@...earbox.net>, <hawk@...nel.org>,
 <john.fastabend@...il.com>, <bpf@...r.kernel.org>, Shannon Nelson
 <shannon.nelson@....com>, Chandan Kumar Rout <chandanx.rout@...el.com>
Subject: Re: [PATCH net 6/8] ice: improve updating ice_{t,
 r}x_ring::xsk_pool

On Wed, 24 Jul 2024 17:49:12 +0200 Maciej Fijalkowski wrote:
> > So if we are already in the af_xdp handler, and update patch sets pool
> > to NULL - the af_xdp handler will be fine with the pool becoming NULL?
> > I guess it may be fine, it's just quite odd to call the function called
> > _ONCE() multiple times..  
> 
> Update path before NULLing pool will go through rcu grace period, stop
> napis, disable irqs, etc. Running napi won't be exposed to nulled pool in
> such case.

Could you make it clearer what condition the patch is fixing, then?
What can go wrong without this patch?