Re: BUG: credit=sched2 machine hang when using DRAKVUF

[Jürgen Groß <jgross@xxxxxxxx>]

On 23.10.20 00:59, Michał Leszczyński wrote:
> Hello,
>
> when using DRAKVUF against a Windows 7 x64 DomU, the whole machine hangs after 
> a few minutes.
>
> The chance for a hang seems to be correlated with number of PCPUs, in this case 
> we have 14 PCPUs and hang is very easily reproducible, while on other machines 
> with 2-4 PCPUs it's very rare (but still occurring sometimes). The issue is 
> observed with the default sched=credit2 and is no longer reproducible once 
> sched=credit is set.
Interesting. Can you please share some more information?

Which Xen version are you using?

Is there any additional information in the dom0 log which could be
related to the hang (earlier WARN() splats, Oopses, Xen related
messages, hardware failure messages, ...?

Can you please try to get backtraces of all cpus at the time of the
hang?

It would help to know which cpu was the target of the call of
smp_call_function_single(), so a disassembly of that function would
be needed to find that information from the dumped registers.

I'm asking because I've seen a similar problem recently and I was
rather suspecting a fifo event channel issue than the Xen scheduler,
but your data suggests it could be the scheduler after all (if it is
the same issue, of course).


Juergen