Re: BUG: soft lockup in __kmalloc_node() with KFENCE enabled

[Marco Elver]

On Mon, 11 Oct 2021 at 11:53, Andrea Righi <andrea.righi@xxxxxxxxxxxxx> wrote:
> On Mon, Oct 11, 2021 at 11:23:32AM +0200, Andrea Righi wrote:
> ...
> > > You seem to use the default 20s stall timeout. FWIW syzbot uses 160
> > > secs timeout for TCG emulation to avoid false positive warnings:
> > > https://github.com/google/syzkaller/blob/838e7e2cd9228583ca33c49a39aea4d863d3e36d/dashboard/config/linux/upstream-arm64-kasan.config#L509
> > > There are a number of other timeouts raised as well, some as high as
> > > 420 seconds.
> >
> > I see, I'll try with these settings and see if I can still hit the soft
> > lockup messages.
>
> Still getting soft lockup messages even with the new timeout settings:
>
> [  462.663766] watchdog: BUG: soft lockup - CPU#2 stuck for 430s! [systemd-udevd:168]
> [  462.755758] watchdog: BUG: soft lockup - CPU#3 stuck for 430s! [systemd-udevd:171]
> [  924.663765] watchdog: BUG: soft lockup - CPU#2 stuck for 861s! [systemd-udevd:168]
> [  924.755767] watchdog: BUG: soft lockup - CPU#3 stuck for 861s! [systemd-udevd:171]

The lockups are expected if you're hitting the TCG bug I linked. Try
to pass '-enable-kvm' to the inner qemu instance (my bad if you
already have), assuming that's somehow easy to do.

Thanks,
-- Marco