netdev - Re: [PATCH net-next v3 08/24] ovpn: introduce the ovpn

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Date: Thu, 9 May 2024 15:46:50 +0200
From: Antonio Quartulli <antonio@...nvpn.net>
To: Sabrina Dubroca <sd@...asysnail.net>
Cc: netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
 Sergey Ryazanov <ryazanov.s.a@...il.com>, Paolo Abeni <pabeni@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>, Andrew Lunn <andrew@...n.ch>,
 Esben Haabendal <esben@...nix.com>
Subject: Re: [PATCH net-next v3 08/24] ovpn: introduce the ovpn_socket object

On 09/05/2024 15:32, Sabrina Dubroca wrote:
> 2024-05-08, 22:38:58 +0200, Antonio Quartulli wrote:
>> On 08/05/2024 19:10, Sabrina Dubroca wrote:
>>> 2024-05-06, 03:16:21 +0200, Antonio Quartulli wrote:
>>>> diff --git a/drivers/net/ovpn/socket.c b/drivers/net/ovpn/socket.c
>>>> new file mode 100644
>>>> index 000000000000..a4a4d69162f0
>>>> --- /dev/null
>>>> +++ b/drivers/net/ovpn/socket.c
>>> [...]
>>>> +
>>>> +/* Finalize release of socket, called after RCU grace period */
>>>
>>> kref_put seems to call ovpn_socket_release_kref without waiting, and
>>> then that calls ovpn_socket_detach immediately as well. Am I missing
>>> something?
>>
>> hmm what do we need to wait for exactly? (Maybe I am missing something)
>> The ovpn_socket will survive a bit longer thanks to kfree_rcu.
> 
> The way I read this comment, it says that ovpn_socket_detach will be
> called after one RCU grace period, but I don't see where that grace
> period would come from.
> 
>      ovpn_socket_put -> kref_put(release=ovpn_socket_release_kref) ->
>        ovpn_socket_release_kref -> ovpn_socket_detach
> 
> No grace period here.
> 
> Or am I misinterpreting the comment? There will be a grace period
> caused by kfree_rcu before the ovpn_socket is actually freed, is that
> what the comment means?

Forgive me - only now I realized that you were referring to what the 
comment says.

That comment is just totally busted. I think it was there since the code 
was doing something totally different and was carried over and over by 
mistake.

Sorry

-- 
Antonio Quartulli
OpenVPN Inc.