netdev - Re: [RT PATCH 1/2] net: add back the missing serialization in ip_send_unicast

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Message-ID: <20160831163613.dg5hgb6l2jd5b5ms@linutronix.de>
Date:   Wed, 31 Aug 2016 18:36:14 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, netdev@...r.kernel.org
Subject: Re: [RT PATCH 1/2] net: add back the missing serialization in
 ip_send_unicast_reply()

On 2016-08-31 12:15:53 [-0400], Steven Rostedt wrote:
> > @@ -689,10 +691,13 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb)
> >  		     offsetof(struct inet_timewait_sock, tw_bound_dev_if));
> >  
> >  	arg.tos = ip_hdr(skb)->tos;
> > +
> > +	local_lock(tcp_sk_lock);
> 
> Interesting that I noticed in mainline, they have:
> 
> 	local_bh_disable();
> 
> here.
> 
> I'm surprised we don't have a local_lock_bh() or something to that
> effect.

Turning local_bh_disable() into local_lock_bh(). One side effect would
be that the network driver will be flushed out / waited for completion
during socket write (due to the spin_lock_bh()). Not sure how much fun
all this will bring.
We could try this…

> -- Steve

Sebastian