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Re: [PATCH v1] xen/sched/null: avoid crash after failed domU creation
- To: Juergen Gross <jgross@xxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
- Date: Thu, 18 May 2023 17:27:05 -0400
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- Cc: George Dunlap <george.dunlap@xxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>
- Delivery-date: Thu, 18 May 2023 21:27:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 5/5/23 01:59, Juergen Gross wrote:
> On 01.05.23 22:30, Stewart Hildebrand wrote:
>> When creating a domU, but the creation fails, there is a corner case that may
>> lead to a crash in the null scheduler when running a debug build of Xen.
>>
>> (XEN) ****************************************
>> (XEN) Panic on CPU 0:
>> (XEN) Assertion 'npc->unit == unit' failed at common/sched/null.c:379
>> (XEN) ****************************************
>>
>> The events leading to the crash are:
>>
>> * null_unit_insert() was invoked with the unit offline. Since the unit was
>> offline, unit_assign() was not called, and null_unit_insert() returned.
>> * Later during domain creation, the unit was onlined
>> * Eventually, domain creation failed due to bad configuration
>> * null_unit_remove() was invoked with the unit still online. Since the unit
>> was
>> online, it called unit_deassign() and triggered an ASSERT.
>>
>> To fix this, only call unit_deassign() when npc->unit is non-NULL in
>> null_unit_remove.
>>
>> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
>
> Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Thanks for the review. Does this still need a maintainer ack?
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