disk I/O race condition after update
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
udev (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned |
Bug Description
About 8 times over this cycle, I have installed various versions of 12.04 server edition on a pathetic old test computer.
In addition to the regular testiing, the purpose is to verify minimum system specifications.
The issue raised herein first appeared with the i386 server ISO of 2012.04.12.
The issue remains with an up to date system as of 2012.04.21.
The issue does NOT exist with a fresh install from the i386 server ISO of 2012.03.27, which the most recent preceeding ISO I had.
The issue: Under very intensive disk I/O situations, the system can lock up. Eventually (I think after about 30 seconds, I am actually rarely standing beside the computer when this occurs) the system does realize it is frozen and manages to resume. It appears as though the computer is waiting for some data from the disk, but the disk doesn't think it has anything to do. I.E. they are out of sync. The appropriate lines from kern.log will be attached.
The issue does not appear to be with the kernel itself, because it can be created by starting from the fresh install from the 2012.03.27 ISO and doing "apt-get update" and "apt-get upgrade" but not "apt-get dist-upgrade". I do not know which package introduced the issue, which is why I have not been able to run "ubuntu-bug <packagename>" for this report. I did list them all before any updates and after, and will post both the difference file and my edited difference file, where I took my best guess at editing out ones that I didn;t think would be contain the root cause.
Note also bug number 978384, which seems similar but not the same. Regardless, the test kernel page does have the verion i would need to try.
For testing for this issue I use "sudo update-
This issue has been demonstrated with two older style ATA hard drives. Both drives have been health tested with disk test tools and the system booted from a freedos ISO.
The enitre start from a fresh install from the 2012.03.37 ISO and test and sow no issue and then upgrade and test and show issue has been rpeated several times. This latest test included 8 times running "sudo update-
It is possible that my CPU is the problem, being below the minimum server edition specifications (200 Mhz, whereas mininmum spec is 300 Mhz). However, the CPU is largely idle with these tests, as it mostly waits for disk I/O. (O.K., it also does have some pretty busy periods.)
Attachments will be added over the next hour.
doug@test-
Linux test-smy 3.2.0-23-
doug@test-
Linux version 3.2.0-23-
doug@test-
Description: Ubuntu 12.04 LTS
Release: 12.04
tags: | added: precise |
Changed in linux (Ubuntu): | |
status: | New → Confirmed |
affects: | linux (Ubuntu) → udev (Ubuntu) |
Changed in udev (Ubuntu): | |
importance: | Medium → Undecided |
status: | Confirmed → New |
tags: | removed: bot-comment kernel-bug-exists-upstream |
For these two lines in the edited kern.log.txt file:
Apr 20 23:49:33 test-smy kernel: [ 4662.839710] Clocksource tsc unstable (delta = 303994203 ns)
Apr 20 23:49:33 test-smy kernel: [ 4662.841953] Switching to clocksource pit
I do not think the clock was actually unstable. I think it got out of sync because of the freeze and then was interpreted as unstable. I have no real proof, though.