netdev - Re: [PATCH v3] tcp: Add memory barrier to tcp

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Message-ID: <20240118084020.2326c3ac@kernel.org>
Date: Thu, 18 Jan 2024 08:40:20 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>, Salvatore Dipietro
 <dipiets@...zon.com>, alisaidi@...zon.com, benh@...zon.com,
 blakgeof@...zon.com, davem@...emloft.net, dipietro.salvatore@...il.com,
 dsahern@...nel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3] tcp: Add memory barrier to tcp_push()

On Thu, 18 Jan 2024 11:42:40 +0100 Eric Dumazet wrote:
> > > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > > index ff6838ca2e58..ab9e3922393c 100644
> > > --- a/net/ipv4/tcp.c
> > > +++ b/net/ipv4/tcp.c
> > > @@ -726,6 +726,7 @@ void tcp_push(struct sock *sk, int flags, int mss_now,
> > >               /* It is possible TX completion already happened
> > >                * before we set TSQ_THROTTLED.
> > >                */
> > > +             smp_mb__after_atomic();  
> >
> > Out of sheer ignorance I'm wondering if moving such barrier inside the
> > above 'if' just after 'set_bit' would suffice?  
> 
> I think this would work just fine.

Sorry, "this" as in Paolo's suggestion or "this" as in the v3 patch 
as posted? :)