From: Avi Kivity <avi@redhat.com>
To: qemu-devel@nongnu.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH]: fix QEMU SCSI lock up
Date: Thu, 25 Sep 2008 11:00:25 +0300 [thread overview]
Message-ID: <48DB4519.6040902@redhat.com> (raw)
In-Reply-To: <48DACF6F.40301@us.ibm.com>
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.
next prev parent reply other threads:[~2008-09-25 7:58 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-24 22:59 [Qemu-devel] [PATCH]: fix QEMU SCSI lock up Marcelo Tosatti
2008-09-24 23:38 ` [Qemu-devel] " Anthony Liguori
2008-09-25 8:00 ` Avi Kivity [this message]
2008-10-16 15:25 ` Avi Kivity
2008-10-21 14:57 ` Anthony Liguori
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