Bug 1205529
| Summary: | Race prevents qemu from getting kernel output | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Stef Walter <stefw> |
| Component: | qemu | Assignee: | Fedora Virtualization Maintainers <virt-maint> |
| Status: | CLOSED INSUFFICIENT_DATA | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | 22 | CC: | amit.shah, berrange, cfergeau, dperpeet, dwmw2, itamar, jscotka, mvollmer, pbonzini, rjones, scottt.tw, stefw, virt-maint |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2015-04-01 14:43:50 UTC | Type: | Bug |
| 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: | 1204627 | ||
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Description
Stef Walter
2015-03-25 06:44:01 UTC
This breaks Cockpit development. Is there a reproducer which isn't "Run the Cockpit CI suite". I can pretty much guarantee that no one will investigate this bug without considerably more information, like the qemu command line being used and how you're expecting to get the console messages and so forth. Ideally I'd want to see a qemu command line which can be run that demonstrates the loss of console messages intermittently, eg: $ qemu-kvm -nodefaults -nographic -m 1024 -kernel /boot/vmlinuz-XXX -append "console=ttyS0" -serial stdio FWIW here is a simple libguestfs-based test you can try: $ libguestfs-test-tool We have never seen intermittent lost console messages however. > I can pretty much guarantee that no one will investigate this bug
without considerably more information,
Indeed, and I wanted to see what kind of information to provide. Thanks for the notes, that's a good place to get started.
I've started trying to 'tee' the output from qemu. This may have caused a heisenbug situation, where the tee file descriptor reading behavior causes the bug to go away. Will keep you posted. In the meantime, this is the sort of qemu command line we're running: qemu-kvm -m 1024 -drive if=virtio,file=/data/src/cockpit/test/run/cockpit-fedora-22-x86_64-root,index=0,serial=ROOT,snapshot=on -kernel /data/src/cockpit/test/run/cockpit-fedora-22-x86_64-kernel -initrd /data/src/cockpit/test/run/cockpit-fedora-22-x86_64-initrd -append 'root=/dev/vda console=ttyS0 quiet ' -nographic -net nic,model=virtio,macaddr=52:54:00:9e:00:00 -net bridge,vlan=0,br=cockpit0 -device virtio-scsi-pci,id=hot -monitor unix:path=/data/src/cockpit/test/run/machine-lKrTWb.mon,server,nowait We continue to see this behavior off and on. We had to refactor our test suite so we didn't depend on qemu console output. But again, that doesn't help you debug this ... so I can close this for now. Sorry about that. I have a very unreliable reproducer that I was meaning to upload and link to... http://files.cockpit-project.org/~mvo/bootlog-reproducer.tar.xz (Warning, 600 MB.) Instructions: Untar it and cd into the directory. $ sudo ./vm-prep $ ./check-example This will very occasionally time out while waiting for a certain boot message. You might try this: $ while ./check-example; do true; done At this point, my personal hunch is that it's actually usually Fedora 22 that sometimes fails to output boot messages, but we have definitely also seen breakage with a Fedora 21 image. With Fedora 22, we always see the final "<hostname> login: " output, but sometimes no "[ OK ] Starting BlitzGewitter" etc messages. With Fedora 21, we used to sometimes not see any output. This is what made us think that the breakage happens in qemu. |