Re: [Xen-devel] [BUG] XEN crash and double fault when doing cpu online/offline

[Jürgen Groß <jgross@xxxxxxxx>]

On 08.01.20 06:50, Tao Xu wrote:
> Hi,
>
> When I use xen-hptool cpu-offline/cpu-online to let CPU in a socket 
> online/offline using the script as follows:
> for((j=48;j<=95;j++));
> do
>    xen-hptool cpu-offline $j
> done
>
> for((j=48;j<=95;j++));
> do
>    xen-hptool cpu-online $j
> done
>
> Xen crash when cpu re-online. I use the upstream XEN(0dd92688) and try 
> many days, it still crash. But if I only do cpu online/offline for CPU 
> 48~59, Xen will not crash. The bug can be reproduced when we do cpu 
> online/offline for most CPU in a socket. And interesting thing is when 
> we use the script as follow:
> for((j=48;j<=95;j++));
> do
>    xen-hptool cpu-offline $j
>    xen-hptool cpu-online $j
> done
>
> Xen will not crash too. Is there a bug in sched_credit2?
>
> The crash message as follows:
>
> (XEN) Adding cpu 77 to runqueue 1
> (XEN) Adding cpu 78 to runqueue 1
> (XEN) Adding cpu 79 to runqueue 1
> (XEN) Adding cpu 80 to runqueue 1
> (X(ENXE) N) *** DOUBLE FAULT ***
> (XEN) Assertion 'debug->cpu == smp_processor_id()' failed at spinlock.c:88
> (XEN) ----[ Xen-4.14-unstable  x86_64  debug=y   Not tainted ]----
> (XEN) Debugging connection not set up.
> (XEN) CPU:    48
> (XEN) ----[ Xen-4.14-unstable  x86_64  debug=y   Not tainted ]----
> (XEN) CPU:    0
> (XEN) RIP:    e008:[<ffff82d080240bfc>] _spin_unlock+0x40/0x42
So the original problem causes a double fault, but spinlock debugging
causes a subsequent panic.

Can you please retry the tests with the attached patch? It should
result in diagnostic data related to the real problem.


Juergen

Attachment: 0001-xen-spinlock-disable-spinlock-debugging-in-console_f.patch
Description: Text Data

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