netdev - Re: [PATCH net] net: add RCU protection to (struct packet

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Message-ID: <CANn89iJRmEPJiz5-L_yJorU+xH5kBwraFy2_-=TwgkHzzfjKEg@mail.gmail.com>
Date: Mon, 2 Feb 2026 10:14:38 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: "dongchenchen (A)" <dongchenchen2@...wei.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	fengwei_yin@...ux.alibaba.com, zhangchangzhong@...wei.com
Subject: Re: [PATCH net] net: add RCU protection to (struct packet_type)->dev

On Mon, Feb 2, 2026 at 9:47 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Mon, Feb 2, 2026 at 9:21 AM dongchenchen (A)
> <dongchenchen2@...wei.com> wrote:
> >
> >
> > }
> >
> > [2] add delay to pype_seq_next
> > diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
> > index 160dd729178f..73f5a20ef57c 100644
> > --- a/net/core/net-procfs.c
> > +++ b/net/core/net-procfs.c
> > @@ -230,11 +230,14 @@ static void *ptype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
> >
> >          pt = v;
> >          nxt = pt->list.next;
> > +       if (pt->dev)
> > +               mdelay(5000);
>
> Waiting 5 seconds while holding RCU is going to fire the soft lockup
> detection after ~two calls to ptype_seq_next()
>
> What is the actual trace you got, and what happens if you reduce to
> mdelay(1000) ?

OK, I took a look, and ptype_get_idx() needs to return information
about what list the returned pt is in.

I will send a V2 ,thanks.