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

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Message-ID: <CAHS8izN=fPj+yMqZBFX83Bvbvpr-fXNnuN_GDq0eVXTOeB7aWg@mail.gmail.com>
Date: Tue, 11 Mar 2025 16:43:26 -0700
From: Mina Almasry <almasrymina@...gle.com>
To: Stanislav Fomichev <stfomichev@...il.com>
Cc: Stanislav Fomichev <sdf@...ichev.me>, 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 1:03 PM Stanislav Fomichev <stfomichev@...il.com> wrote:
>
> On 03/11, Mina Almasry wrote:
> > 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)?
>
> Right, if I acquire it later, I'd have to do the same order
> in netdev_nl_sock_priv_destroy and it seems to be a bit more complicated
> to do (since we go over the list of bindings over there).

Thanks,

Reviewed-by: Mina Almasry <almasrymina@...gle.com>


-- 
Thanks,
Mina