Bug 770919
| Summary: | Sometimes virsh command screenshot may hang | ||
|---|---|---|---|
| Product: | Red Hat Enterprise Linux 6 | Reporter: | weizhang <weizhan> |
| Component: | libvirt | Assignee: | Michal Privoznik <mprivozn> |
| Status: | CLOSED ERRATA | QA Contact: | Virtualization Bugs <virt-bugs> |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 6.3 | CC: | acathrow, dallan, dyuan, honzhang, mzhan, rwu, yupzhang |
| Target Milestone: | rc | ||
| Target Release: | --- | ||
| Hardware: | x86_64 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | libvirt-0.9.10-1.el6 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2012-06-20 06:40:30 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: | |||
When I set log_level=1 on libvirtd.conf and then restart libvirtd, it will not hang any more on loop execution Patch sent upstream: https://www.redhat.com/archives/libvir-list/2012-January/msg00343.html NB, this is not restricted to screenshot only, but any API using streams could have hit this issue. But yeah, all other stream using APIs do take longer time to finish, so screenshot is perfect for verification and testing. Moving to POST:
commit 833b901cb711a9db148b4fe39e658411f82f3467
Author: Michal Privoznik <mprivozn>
AuthorDate: Tue Jan 10 16:57:30 2012 +0100
Commit: Michal Privoznik <mprivozn>
CommitDate: Thu Jan 12 12:02:40 2012 +0100
stream: Check for stream EOF
If client stream does not have any data to sink and neither received
EOF, a dummy packet is sent to the daemon signalising client is ready to
sink some data. However, after we added event loop to client a race may
occur:
Thread 1 calls virNetClientStreamRecvPacket and since no data are cached
nor stream has EOF, it decides to send dummy packet to server which will
sent some data in turn. However, during this decision and actual message
exchange with server -
Thread 2 receives last stream data from server. Therefore an EOF is set
on stream and if there is a call waiting (which is not yet) it is woken
up. However, Thread 1 haven't sent anything so far, so there is no call
to be woken up. So this thread sent dummy packet to daemon, which
ignores that as no stream is associated with such packet and therefore
no reply will ever come.
This race causes client to hang indefinitely.
v0.9.9-30-g833b901
Reproduce the bug using libvirt-0.9.9-1.el6.x86_64
Verify it using libvirt-0.9.10-1.el6.x86_64
Steps
1. Prepare a running guest
2. # for i in {1..100}; do virsh screenshot guest; sleep 1; done
Results
Command executed without hang
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHSA-2012-0748.html |
Description of problem: Sometimes virsh command screenshot may hang Version-Release number of selected component (if applicable): kernel-2.6.32-223.el6.x86_64 libvirt-0.9.9-0rc1.el6.x86_64 qemu-kvm-0.12.1.2-2.213.el6.x86_64 How reproducible: sometimes Steps to Reproduce: 1. Prepare a running guest 2. # for i in {1..100}; do virsh screenshot guest; sleep 1; done 3. Actual results: It may hang after several loops Expected results: Command executed without hang Additional info: