linux-kernel - Re: Kernel Panic in skb_release

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Date:   Fri, 28 May 2021 18:32:19 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Doug Berger <opendmb@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>
Subject: Re: Kernel Panic in skb_release_data using genet

hi Florian,

On Fri, May 28, 2021 at 09:21:27AM -0700, Florian Fainelli wrote:
> On 5/24/21 8:37 AM, Florian Fainelli wrote:
> > 
> > 
> > On 5/24/2021 8:13 AM, Maxime Ripard wrote:
> >> Hi Florian,
> >>
> >> On Mon, May 24, 2021 at 07:49:25AM -0700, Florian Fainelli wrote:
> >>> Hi Maxime,
> >>>
> >>> On 5/24/2021 6:01 AM, Maxime Ripard wrote:
> >>>> Hi Doug, Florian,
> >>>>
> >>>> I've been running a RaspberryPi4 with a mainline kernel for a while,
> >>>> booting from NFS. Every once in a while (I'd say ~20-30% of all boots),
> >>>> I'm getting a kernel panic around the time init is started.
> >>>>
> >>>> I was debugging a kernel based on drm-misc-next-2021-05-17 today with
> >>>> KASAN enabled and got this, which looks related:
> >>>
> >>> Is there a known good version that could be used for bisection or you
> >>> just started to do this test and you have no reference point?
> >>
> >> I've had this issue for over a year and never (I think?) got a good
> >> version, so while it might be a regression, it's not a recent one.
> > 
> > OK, this helps and does not really help.
> > 
> >>
> >>> How stable in terms of clocking is the configuration that you are using?
> >>> I could try to fire up a similar test on a Pi4 at home, or use one of
> >>> our 72112 systems which is the closest we have to a Pi4 and see if that
> >>> happens there as well.
> >>
> >> I'm not really sure about the clocking. Is there any clock you want to
> >> look at in particular?
> > 
> > ARM, DDR, AXI, anything that could cause some memory corruption to occur
> > essentially. GENET clocks are fairly fixed, you have a 250MHz clock and
> > a 125MHz clock feeding the data path.
> > 
> >>
> >> My setup is fairly simple: the firmware and kernel are loaded over TFTP
> >> and the rootfs is mounted over NFS, and the crash always occur around
> >> init start, so I guess when it actually starts to transmit a decent
> >> amount of data?
> > 
> > Do you reproduce this problem with KASAN disabled, do you eventually
> > have a crash pointing back to the same location?
> > 
> > I have a suspicion that this is all Pi4 specific because we regularly
> > run the GENET driver through various kernel versions (4.9, 5.4 and 5.10
> > and mainline) and did not run into that.
> 
> I have not had time to get a set-up to reproduce what you are seeing,
> could you share your .config meanwhile? Thanks

Sorry, I didn't have the time to check how the clock were behaving.

You'll find attached my config.txt file and .config

I'm booting the board entirely from TFTP (which might introduce some
issues in the "handoff" from the bootloader to the kernel), you'll find
some guide there:

https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/net_tutorial.md

Maxime

View attachment "config-mainline" of type "text/plain" (199478 bytes)

View attachment "config.txt" of type "text/plain" (1498 bytes)

Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)