Bug 504910
| Summary: | Command "virsh save <domain> <file>" hang when trying to save a paused domain on xen | ||||||||
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| Product: | Red Hat Enterprise Linux 5 | Reporter: | Edward Wang <edwang> | ||||||
| Component: | xen | Assignee: | Michal Novotny <minovotn> | ||||||
| Status: | CLOSED ERRATA | QA Contact: | Virtualization Bugs <virt-bugs> | ||||||
| Severity: | medium | Docs Contact: | |||||||
| Priority: | medium | ||||||||
| Version: | 5.4 | CC: | areis, clalance, minovotn, mshao, pbonzini, rlerch, sghosh, veillard, virt-maint, xen-maint, yshao | ||||||
| Target Milestone: | rc | ||||||||
| Target Release: | --- | ||||||||
| Hardware: | All | ||||||||
| OS: | Linux | ||||||||
| Whiteboard: | |||||||||
| Fixed In Version: | xen-3.0.3-95.el5 | Doc Type: | Bug Fix | ||||||
| Doc Text: |
Save operations should not be attempted on paused Xen domains. This will cause Xend to hang.
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Story Points: | --- | ||||||
| Clone Of: | Environment: | ||||||||
| Last Closed: | 2010-03-30 08:58:35 UTC | Type: | --- | ||||||
| Regression: | --- | Mount Type: | --- | ||||||
| Documentation: | --- | CRM: | |||||||
| Verified Versions: | Category: | --- | |||||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||||
| Embargoed: | |||||||||
| Bug Depends On: | |||||||||
| Bug Blocks: | 513501 | ||||||||
| Attachments: |
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Description
Edward Wang
2009-06-10 02:13:21 UTC
Can you try the same steps, but instead of 'virsh save', use 'xm save' instead. This will determine if the bug is in libvirt or XenD. Daniel, I've tried 'xm save' (the other steps are the same with above), the result is the same, that is: 1, The 'xm save' process hangs 2, Find two domains with the SAME name exist in the output of "virsh list --all", one is 'paused', another is 'shut off' If still need other information, just let me know. Thanks a lot Release note added. If any revisions are required, please set the "requires_release_notes" flag to "?" and edit the "Release Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Save operations should not be attempted on paused Xen domains. This will cause Xend to hang. I am taking this one, patch will be coming soon... Created attachment 348908 [details]
Xm save hang on saving paused domain fix
This is the patch/workaround for this bug. The problem is that xend was waiting until the domain shuts down when doing save but this condition never happened because of domain was unable to shutdown in paused state. Therefore the domain must be unpaused before doing save and my patch checks the domain state and if it's paused, it unpauses the domain to allow shutdown. After that, everything works fine and the domain is saved.
I've tried it about 10 times and xend never hung.
Michal
I'm not sure of whether this is a good fix, unfortunately. The machine will restart for a very short while, but it was presumably paused for a reason... :-( Yeah, we discussed this on the mailing list, I should have updated it here. You are right, it's a bad idea to unpause the domain behind the administrator's back. Basically, we should just fail with a message saying "Can't save since the domain is paused; unpause it first if you want to save", and just abort. Chris Lalancette Yeah, we could write some error message from XenD itself but it makes a perfect sense - when a domain is paused, it can't start shutting down because shutdown is just issuing a shutdown domain in the domain itself. Should I create a patch to write just an error when trying to shutdown paused domain? Well, it's paused for the reason but what administrator would do if he really wants to shut the domain down? He unpauses it and issues shutdown then so this could be annoying for administrators because unpausing the domain is necessary to issue just one last command - the shutdown command. This is in fact what does one step for administrator - not to annoy administrators with message that he needs to unpause it first. In fact if I imagine myself being a system administrator wanting to shut it down I'd prefer xend doing this for me and not telling me I need to unpause it manually in order to allow shutdown. Maybe, this should be configurable in xend-config.sxp file... something like: (allow-domain-unpause-before-shutdown yes) or something similar... Administrators should then choose whether to display only a message (when set to "no") or to unpause the domain automatically when issuing a shutdown command on paused domain. What do you think about this suggestion ? > Well, it's paused for the reason but what administrator would do if he really
> wants to shut the domain down?
For example, kvm will save the machine and then restore it as paused (actually it's buggy, but I have that bug). The key point here is that the domain is not shutdown, it is destroyed when you save (unless I'm mistaken). So in theory it should be possible to make it work.
I agree with Chris that for Xen an error message is the best course of action. Even just printing a message and hanging (the administrator can then unpause the VM from another terminal or after ^Z) does not seem too bad, though I'm not sure about it.
(In reply to comment #11) > > Well, it's paused for the reason but what administrator would do if he really > > wants to shut the domain down? > > For example, kvm will save the machine and then restore it as paused (actually > it's buggy, but I have that bug). The key point here is that the domain is not > shutdown, it is destroyed when you save (unless I'm mistaken). So in theory it > should be possible to make it work. > > I agree with Chris that for Xen an error message is the best course of action. > Even just printing a message and hanging (the administrator can then unpause > the VM from another terminal or after ^Z) does not seem too bad, though I'm not > sure about it. I see your point. I am not thinking it's bad but if I would like to shut it down, I'd prefer it configurable to either show error message or do the unpause for me. (In reply to comment #12) > (In reply to comment #11) > > > Well, it's paused for the reason but what administrator would do if he really > > > wants to shut the domain down? > > > > For example, kvm will save the machine and then restore it as paused (actually > > it's buggy, but I have that bug). The key point here is that the domain is not > > shutdown, it is destroyed when you save (unless I'm mistaken). So in theory it > > should be possible to make it work. > > > > I agree with Chris that for Xen an error message is the best course of action. > > Even just printing a message and hanging (the administrator can then unpause > > the VM from another terminal or after ^Z) does not seem too bad, though I'm not > > sure about it. > > I see your point. I am not thinking it's bad but if I would like to shut it > down, I'd prefer it configurable to either show error message or do the unpause > for me. You don't want to do things behind the administrators back. While we could add an option to do it for the administrator, the fact of the matter is that very few people use this functionality, so it's complete overkill. Just having a message that says "unpause before you save/shutdown" is safe, easy, and straightforward. Chris Lalancette (In reply to comment #13) > (In reply to comment #12) > > (In reply to comment #11) > > > > Well, it's paused for the reason but what administrator would do if he really > > > > wants to shut the domain down? > > > > > > For example, kvm will save the machine and then restore it as paused (actually > > > it's buggy, but I have that bug). The key point here is that the domain is not > > > shutdown, it is destroyed when you save (unless I'm mistaken). So in theory it > > > should be possible to make it work. > > > > > > I agree with Chris that for Xen an error message is the best course of action. > > > Even just printing a message and hanging (the administrator can then unpause > > > the VM from another terminal or after ^Z) does not seem too bad, though I'm not > > > sure about it. > > > > I see your point. I am not thinking it's bad but if I would like to shut it > > down, I'd prefer it configurable to either show error message or do the unpause > > for me. > > You don't want to do things behind the administrators back. While we could add > an option to do it for the administrator, the fact of the matter is that very > few people use this functionality, so it's complete overkill. Just having a > message that says "unpause before you save/shutdown" is safe, easy, and > straightforward. > > Chris Lalancette Of course it depends on how often this is used. I can just display a message, that's right and easy - the thing was just to make administrator choose what does he want in the config file. But since it's now a very used feature, it's overkill and therefore displaying the message is good. Michal Created attachment 351557 [details]
Error message when shutting down/saving paused domain
This is patch to display just error message when issuing domain shutdown - the shutdown is called when saving too. It can't shutdown when it's paused and not to unpause the domain behind administrators back (like first version of this patch did), this just shows the error message.
Fix built into xen-3.0.3-95.el5 When I try to save a paused domain on xen, it will pop out a message like: "Error: Can't shutdown/save the domain since the domain is paused; unpaused it first if you want to shutdown/save". Base on the comment #15, so this bug is verified in xen-3.0.3-102.el5. An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHBA-2010-0294.html This bug was closed during 5.5 development and it's being removed from the internal tracking bugs (which are now for 5.6). |