From: David Hildenbrand <david@redhat.com>
To: Keqian Zhu <zhukeqian1@huawei.com>,
qemu-devel@nongnu.org, Peter Maydell <peter.maydell@linaro.org>,
Igor Mammedov <imammedo@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>
Cc: wanghaibin.wang@huawei.com, Zenghui Yu <yuzenghui@huawei.com>,
jiangkunkun@huawei.com, salil.mehta@huawei.com
Subject: Re: [PATCH v1 2/2] system/cpus: Fix resume_all_vcpus() under vCPU hotplug condition
Date: Mon, 18 Mar 2024 11:14:30 +0100 [thread overview]
Message-ID: <57c8506e-3f6a-4d1d-9720-c9b030781109@redhat.com> (raw)
In-Reply-To: <20240317083704.23244-3-zhukeqian1@huawei.com>
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
next prev parent reply other threads:[~2024-03-18 10:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-17 8:37 [PATCH v1 0/2] Some fixes for pause and resume all vcpus Keqian Zhu via
2024-03-17 8:37 ` [PATCH v1 1/2] system/cpus: Fix pause_all_vcpus() under concurrent environment Keqian Zhu via
2024-03-18 10:10 ` David Hildenbrand
2024-03-19 5:06 ` 答复: " zhukeqian via
2024-03-19 9:24 ` David Hildenbrand
2024-03-19 13:23 ` David Hildenbrand
2024-03-19 14:23 ` Peter Maydell
2024-03-19 14:46 ` David Hildenbrand
2024-03-19 14:56 ` Peter Maydell
2024-03-17 8:37 ` [PATCH v1 2/2] system/cpus: Fix resume_all_vcpus() under vCPU hotplug condition Keqian Zhu via
2024-03-18 10:14 ` David Hildenbrand [this message]
2024-03-19 5:11 ` 答复: " zhukeqian via
2024-03-19 9:25 ` David Hildenbrand
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