Hi Petr,
Am 05.06.2018 um 19:46 schrieb James Morse:
Hi Petr,
(CC: +Akashi, Marc)
On 05/06/18 09:01, Petr Tesarik wrote:
I have observed hangs after crash on a Raspberry Pi 3 Model B+ board
when a panic kernel is loaded.
kdump is a best-effort thing, it looks like this is a case where the
crashed-kernel can't tear itself down.
Do you have the rest of the stack trace? Was it handling an irq when it decided
to panic?:
https://lkml.org/lkml/2018/3/13/1134
the Raspberry Pi 3 B+ support is very fresh (linux-next). Since i didn't
see a version, i need to doublecheck.
You are actually using linux-next and not the downstream kernel?
I attached a hardware debugger and found
out that all CPU cores were stopped except one which was stuck in the
idle thread. It seems that irq_set_irqchip_state() may sleep, which is
definitely not safe after a kernel panic.
I don't know much about irqchip stuff, but __irq_get_desc_lock() takes a
raw_spin_lock(), and calls gic_irq_get_irqchip_state() which is just poking
around in mmio registers, this should all be safe unless you re-entered the same
code.
If I'm right, then this is broken in general, but I have only ever seen
it on RPi 3 Model B+ (even RPi3 Model B works fine), so the issue may
be more subtle.
Is there a hardware difference around the interrupt controller on these?
@James:
No, but the RPi 3 B has a different USB network chip on board (smsc95xx,
Fast ethernet) instead of lan78xx (Gigabit ethernet).
Stefan
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