Re: Kernel Panic in skb_release_data using genet

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:

quoted

Hi Maxime,

On 5/24/2021 6:01 AM, Maxime Ripard wrote:

quoted

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.

quoted

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.
-- 
Florian