From: Markus Armbruster <armbru@redhat.com>
To: Peter Lieven <pl@kamp.de>
Cc: Kevin Wolf <kwolf@redhat.com>,
Stefan Hajnoczi <stefanha@gmail.com>,
qemu-devel <qemu-devel@nongnu.org>,
qemu block <qemu-block@nongnu.org>
Subject: Re: [Qemu-devel] [Qemu-block] RFC cdrom in own thread?
Date: Thu, 18 Jun 2015 08:57:49 +0200 [thread overview]
Message-ID: <87r3p94i6q.fsf@blackfin.pond.sub.org> (raw)
In-Reply-To: <55825F17.3060205@kamp.de> (Peter Lieven's message of "Thu, 18 Jun 2015 08:03:03 +0200")
Peter Lieven <pl@kamp.de> writes:
> Am 17.06.2015 um 10:35 schrieb Kevin Wolf:
>> Am 16.06.2015 um 17:34 hat Stefan Hajnoczi geschrieben:
>>> On Tue, Jun 16, 2015 at 3:44 PM, Peter Lieven <pl@kamp.de> wrote:
>>>> I wonder how difficult it would be to have the IDE CDROM run in its own
>>>> thread?
>>>> We usually have ISOs mounted on an NFS share as CDROM. Problem: If the NFS
>>>> Share
>>>> goes down, it takes down monitor, qmp, vnc etc. with it.
>>>>
>>>> Maybe its already possible to do this via cmdline args?
>>>>
>>>> Any ideas, comments?
>>> If QEMU hangs in the read/write/flush/discard code path due to NFS
>>> downtime it is a bug.
>>>
>>> QEMU is expected to hang in open/reopen because those are performed in
>>> a blocking fashion.
>>>
>>> Which of these cases applies to what you are seeing? Maybe it can be fixed.
>> Don't forget bdrv_drain_all(), which is called a lot by the monitor. So
>> no matter what you do (and this includes moving to a thread as in a
>> hypothetical "ATAPI dataplane"), you end up with a hang sooner or later.
>
> I will have a look where qemu hangs. The problem exists with an NFS share
> mounted by the kernel and also with libnfs. So it might be a bdrv_drain_all.
> I regularly query info block and info blockstats. Do these commands always
> call bdrv_drain_all()?.
As far as I can tell, they don't.
In general, it's hard to see. Wish it wasn't.
next prev parent reply other threads:[~2015-06-18 6:58 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <55803637.3060607@kamp.de>
2015-06-16 15:34 ` [Qemu-devel] [Qemu-block] RFC cdrom in own thread? Stefan Hajnoczi
2015-06-17 8:35 ` Kevin Wolf
2015-06-18 6:03 ` Peter Lieven
2015-06-18 6:57 ` Markus Armbruster [this message]
2015-06-18 6:39 ` Peter Lieven
2015-06-18 6:59 ` Paolo Bonzini
2015-06-18 7:03 ` Peter Lieven
2015-06-18 7:12 ` Peter Lieven
2015-06-18 7:45 ` Kevin Wolf
2015-06-18 8:30 ` Peter Lieven
2015-06-18 8:42 ` Kevin Wolf
2015-06-18 9:29 ` Peter Lieven
2015-06-18 9:36 ` Stefan Hajnoczi
2015-06-18 9:53 ` Peter Lieven
2015-06-19 13:14 ` Peter Lieven
2015-06-22 9:25 ` Stefan Hajnoczi
2015-06-22 13:09 ` Peter Lieven
2015-06-22 21:54 ` John Snow
2015-06-23 6:36 ` Peter Lieven
2015-08-14 13:43 ` Peter Lieven
2015-08-14 14:08 ` Kevin Wolf
2015-08-14 14:21 ` Peter Lieven
2015-08-14 14:45 ` Peter Lieven
2015-08-15 19:02 ` Peter Lieven
2015-06-18 10:17 ` Peter Lieven
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