netdev - Re: Linux kernel hangs if using RV1108 with MSZ8863 switch with two ports connected

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Date:   Sat, 17 Nov 2018 19:04:11 -0200
From:   Otavio Salvador <otavio.salvador@...ystems.com.br>
To:     andrew@...n.ch
Cc:     netdev@...r.kernel.org, Heiko Stuebner <heiko@...ech.de>,
        david.choi@...rel.com, Andy Yan <andy.yan@...k-chips.com>
Subject: Re: Linux kernel hangs if using RV1108 with MSZ8863 switch with two
 ports connected

Hi Andrew,

On Fri, Nov 16, 2018 at 9:40 PM Andrew Lunn <andrew@...n.ch> wrote:
> On Fri, Nov 16, 2018 at 04:28:29PM -0200, Otavio Salvador wrote:
> > RV1108 GMAC is connected to KSZ8863 port 3 and after kernel boots, I
> > can put an Ethernet cable from my router to the uplink port of
> > KSZ8863, which makes the RV1108 board and a Linux PC connected to the
> > other KSZ8863 port to both get IP addresses.
> >
> > So in this usecase the setup is working fine.
> >
> > However, if the RV1108 board boots with both Ethernet cables to the
> > KSZ8863 switch connected, then the kernel silently hangs.
>
> By silently, you mean it prints nothing at all?

Yes, it prints but suddenly hangs.

> I would try building the kernel with all the lock debugging turned
> on. That might find something even with your working case, if there is
> a potential deadlock.
>
> If the kernel dies very early, you might need to enable "kernel
> low-level debugping print and EARLY_PRINTK, in order to see anything.

The kernel starts booting normally and then hangs like this when two
Ethernet cables are connected to the KSZ8863 switch:
http://dark-code.bulix.org/3xexu5-507563

This has the lock detection, inside kernel hacking, enabled.

Any hint?

-- 
Otavio Salvador                             O.S. Systems
http://www.ossystems.com.br        http://code.ossystems.com.br
Mobile: +55 (53) 9 9981-7854          Mobile: +1 (347) 903-9750