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Re: [Qemu-devel] Re: [PATCH]: fix QEMU SCSI lock up
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] Re: [PATCH]: fix QEMU SCSI lock up |
Date: |
Thu, 25 Sep 2008 11:00:25 +0300 |
User-agent: |
Thunderbird 2.0.0.16 (X11/20080723) |
Anthony Liguori wrote:
>>
>> For reasons that I do not fully understand, bdrv_aio_read() does
>> not return immediately, but instead it calls scsi_read_data()
>> recursively.
>
> This bothers me. bdrv_aio_read() should never immediately invoke the
> callback to prevent exactly this sort of problem. Perhaps this was a
> bug that has since been fixed? Is this still reproducible?
qcow2 metadata is synchronous, and if the disk is empty, there will be
no data I/O, so bdrv_aio_read() will never be invoked.
Maybe we should fix this in qcow2 (and the other block formats) by
scheduling a BH.
--
Do not meddle in the internals of kernels, for they are subtle and quick to
panic.