15-march.img hangs at boot on BB-Green

[Ian Lepore]

On Mon, 2018-03-19 at 10:53 +0100, Nicola Mingotti wrote:
> Hi,
> 
> With latest 15-March img relase I am able to boot on BeagleBone Green
> but still, the boot precess hangs at this point, it seems Ethernet related.
> 
> ------------------------ last messages I see on serial console 
> ----------------------
> cpswss0: <3-port Switch Ethernet Subsystem> mem 
> 0x4a100000-0x4a1007ff,0x4a101200-0x4a1012ff irq 38,39,40,41 on simplebus0
> cpswss0: CPSW SS Version 1.12 (0)
> cpswss0: Initial queue size TX=128 RX=384
> cpswss0: Unable to fill RX queue
> cpsw0:  on cpswss0
> --------------------------------------------------------------------------------------------------
> 
> Bye
> Nicola

Today I finally found some time to do some testing with this. It
appears to have broken with r328916 on Feb 6. From then through r328981
the kernel page faults early in boot. Starting with r328982 the fault
is fixed but we get this new problem with the "Unable to fill RX queue"
followed by a hang. The "unable to fill" is caused by an
m_getcl(M_NOWAIT) returning NULL. The hang is caused by a
malloc(M_WAITOK) in if_alloc() hanging forever.

The only other useful info I have so far is that this only happens with
the GENERIC kernel. If you build a kernel using the BEAGLEBONE config
it boots normally.

I don't really know what to do next to debug further. I can insert a
kdb_enter() right before the if_alloc() call that hangs, but I don't
know what to look for in the debugger.

-- Ian