Re: [PATCH v1 2/2] system/cpus: Fix resume_all_vcpus() under vCPU hotplug condition

[David Hildenbrand]

On 17.03.24 09:37, Keqian Zhu via wrote:
> For vCPU being hotplugged, qemu_init_vcpu() is called. In this
> function, we set vcpu state as stopped, and then wait vcpu thread
> to be created.
>
> As the vcpu state is stopped, it will inform us it has been created
> and then wait on halt_cond. After we has realized vcpu object, we
> will resume the vcpu thread.
>
> However, during we wait vcpu thread to be created, the bql is
> unlocked, and other thread is allowed to call resume_all_vcpus(),
> which will resume the un-realized vcpu.
>
> This fixes the issue by filter out un-realized vcpu during
> resume_all_vcpus().

Similar question: is there a reproducer?

How could we currently hotplug a VCPU, and while it is being created, 
see pause_all_vcpus()/resume_all_vcpus() getting claled.

If I am not getting this wrong, there seems to be some other mechanism 
missing that makes sure that this cannot happen. Dropping the BQL 
half-way through creating a VCPU might be the problem.

--
Cheers,

David / dhildenb