linux-kernel - Re: [PATCH net-next v2 2/3] net: add granular lock for the netdev netlink socket

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Message-ID: <CAHS8izNVZ0RqccDKGiL2h+MesCrvza_kwck0RmsrTNAcTkcmjA@mail.gmail.com>
Date: Tue, 11 Mar 2025 08:30:41 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Stanislav Fomichev <sdf@...ichev.me>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, linux-kernel@...r.kernel.org, 
	donald.hunter@...il.com, horms@...nel.org, michael.chan@...adcom.com, 
	pavan.chebbi@...adcom.com, andrew+netdev@...n.ch, jdamato@...tly.com, 
	xuanzhuo@...ux.alibaba.com, asml.silence@...il.com, dw@...idwei.uk
Subject: Re: [PATCH net-next v2 2/3] net: add granular lock for the netdev
 netlink socket

On Tue, Mar 11, 2025 at 7:40 AM Stanislav Fomichev <sdf@...ichev.me> wrote:
>
> As we move away from rtnl_lock for queue ops, introduce
> per-netdev_nl_sock lock.
>
> Cc: Mina Almasry <almasrymina@...gle.com>
> Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
> ---
>  include/net/netdev_netlink.h | 1 +
>  net/core/netdev-genl.c       | 6 ++++++
>  2 files changed, 7 insertions(+)
>
> diff --git a/include/net/netdev_netlink.h b/include/net/netdev_netlink.h
> index 1599573d35c9..075962dbe743 100644
> --- a/include/net/netdev_netlink.h
> +++ b/include/net/netdev_netlink.h
> @@ -5,6 +5,7 @@
>  #include <linux/list.h>
>
>  struct netdev_nl_sock {
> +       struct mutex lock;
>         struct list_head bindings;
>  };
>
> diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
> index a219be90c739..63e10717efc5 100644
> --- a/net/core/netdev-genl.c
> +++ b/net/core/netdev-genl.c
> @@ -859,6 +859,7 @@ int netdev_nl_bind_rx_doit(struct sk_buff *skb, struct genl_info *info)
>                 goto err_genlmsg_free;
>         }
>
> +       mutex_lock(&priv->lock);

You do not need to acquire this lock so early, no? AFAICT you only
need to lock around:

list_add(&binding->list, sock_binding_list);

Or is this to establish a locking order (sock_binding_list lock before
the netdev lock)?

-- 
Thanks,
Mina