Hung task warnings while rebuilding two mdadm RAID arrays

[Danilo Piazzalunga]

I have the following RAID configuration: md0 is a RAID1 array used as the root file system, md1 is another RAID1 array used as swap.

= /proc/mdstat =
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb2[1]
      3020096 blocks [2/1] [_U]

md0 : active raid1 sdb1[1]
      23037056 blocks [2/1] [_U]

unused devices: <none>

I had added the missing devices to their arrays (respectively, sda5 to md0 and sda6 to md1), triggering a spare rebuild for both arrays, and, some minutes later, the system froze. The relevant section of /var/log/messages is attached: unfortunately, the kernel dump is not complete.
Update: the system did not freeze when the problem was reproduced a second time; therefore, just report the warnings about the hung task.

Using Intrepid Ibex Alpha4 + updates, linux kernel 2.6.26-5-generic

[Danilo Piazzalunga (danilopiazza)]

This is the /var/log/syslog snippet, which contains more information:

[ 502.662369] INFO: task md1_resync:6278 blocked for more than 120 seconds.
[ 502.662380] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

[Danilo Piazzalunga (danilopiazza)]

And this is the result from another run: the problem is reproducible, but this time the system did not freeze and continued to perform normally.

[Leann Ogasawara (leannogasawara)]

Hi Danilo,

The Ubuntu Kernel Team is planning to move to the 2.6.27 kernel for the upcoming Intrepid Ibex 8.10 release. As a result, the kernel team would appreciate it if you could please test this newer 2.6.27 Ubuntu kernel. There are one of two ways you should be able to test:

1) If you are comfortable installing packages on your own, the linux-image-2.6.27-* package is currently available for you to install and test.

--or--

2) The upcoming Alpha5 for Intrepid Ibex 8.10 will contain this newer 2.6.27 Ubuntu kernel. Alpha5 is set to be released Thursday Sept 4. Please watch http://www.ubuntu.com/testing for Alpha5 to be announced. You should then be able to test via a LiveCD.

Please let us know immediately if this newer 2.6.27 kernel resolves the bug reported here or if the issue remains. More importantly, please open a new bug report for each new bug/regression introduced by the 2.6.27 kernel and tag the bug report with 'linux-2.6.27'. Also, please specifically note if the issue does or does not appear in the 2.6.26 kernel. Thanks again, we really appreicate your help and feedback.

[Danilo Piazzalunga (danilopiazza)]

After installing and testing with the newer 2.6.27 kernel, I cannot reproduce this anymore, not even with the 2.6.26 kernel.

[Leann Ogasawara (leannogasawara)]

Thanks for the update. It seems 2.6.27 has resolved this issue. Were there any updates to 2.6.26 that you noticed that may have installed which resolved this for 2.6.26 as well? Regradless I'll go ahead and mark this "Fix Released". If you notice any regressions, feel free to set the status back to "New". Thanks.

[Danilo Piazzalunga (danilopiazza)]

I simply could not reproduce this anymore, neither with 2.6.26-5 (using the same kernel which I showed the bug in the first place), nor with 2.6.27. I almost suspect a hardware-induced failure