netdev - Re: [PATCH net] net: bridge: annotate data-race in br_fdb

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Message-ID: <CANn89iL8-e_jphcg49eX=zdWrOeuA-AJDL0qhsTrApA4YnOFEg@mail.gmail.com>
Date: Wed, 7 Jan 2026 09:09:32 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Nikolay Aleksandrov <razor@...ckwall.org>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, 
	eric.dumazet@...il.com
Subject: Re: [PATCH net] net: bridge: annotate data-race in br_fdb_update()

On Wed, Jan 7, 2026 at 8:03 AM Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>
> On 07/01/2026 09:00, Nikolay Aleksandrov wrote:
> > On 06/01/2026 23:26, Nikolay Aleksandrov wrote:
> >> On 06/01/2026 21:40, Eric Dumazet wrote:
> >>> fdb->updated is read and written locklessly.
> >>>
> >>> Add READ_ONCE()/WRITE_ONCE() annotations.
> >>>
> >>> Fixes: 31cbc39b6344 ("net: bridge: add option to allow activity
> >>> notifications for any fdb entries")
> >>> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> >>> Cc: Nikolay Aleksandrov <razor@...ckwall.org>
> >>> ---
> >>>   net/bridge/br_fdb.c | 4 ++--
> >>>   1 file changed, 2 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
> >>> index
> >>> 58d22e2b85fc3551bd5aec9c20296ddfcecaa040..e7bd20f0e8d6b7b24aef43d7bed34adf171c34a8 100644
> >>> --- a/net/bridge/br_fdb.c
> >>> +++ b/net/bridge/br_fdb.c
> >>> @@ -1002,8 +1002,8 @@ void br_fdb_update(struct net_bridge *br,
> >>> struct net_bridge_port *source,
> >>>               unsigned long now = jiffies;
> >>>               bool fdb_modified = false;
> >>> -            if (now != fdb->updated) {
> >>> -                fdb->updated = now;
> >>> +            if (now != READ_ONCE(fdb->updated)) {
> >>> +                WRITE_ONCE(fdb->updated, now);
> >>>                   fdb_modified = __fdb_mark_active(fdb);
> >>>               }
> >>
> >> Thanks,
> >> Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>
> >
> > Actually on second thought, ->updated is used lockless in a few more
> > places, e.g. br_fdb_fillbuf(), fdb_fill_info(), br_fdb_cleanup().
> >
>
> I mean I see the subject, but since this patch will get backported
> perhaps we can annotate all instances in one go.

Sure, I will send a V2, thanks.