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Date: Sun, 17 Aug 2014 10:12:53 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] the whole virtual machine hangs when IO does not
 come back!
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To: "Gonglei (Arei)" <arei.gonglei@huawei.com>, "Wubin (H)" <wu.wubin@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>, "Zhangmin (Rudy)" <rudy.zhangmin@huawei.com>, "Huangpeng (Peter)" <peter.huangpeng@huawei.com>, "stefanha@redhat.com" <stefanha@redhat.com>

Il 11/08/2014 13:39, Gonglei (Arei) ha scritto:
>> I think the VM hangs there because the  VCPU thread holds the global
>> qemu metux lock and waits for IO to come back. However,  in my test, the
>> IO doesn't come back (because of the multipath software). Therefore, the
>> VCPU thread never releases the global lock, and other threads can never
>> get the lock. Is there any idea to solve the whole vm hanging problem?

The problem is that qemu_aio_cancel is a synchronous function.

You can work around it with an eh_times_out function in the virtio-scsi
driver, but the real fix would be in QEMU.

Paolo

>> I also did the same test on the VMware platform, the IO hangs but the VM
>> is still working. Thanks!
>>
>