/sbin/mdadm --examine --scan --config=partitions hangs in RAIDVERSION ioctl

[Mathieu Trudel-Lapierre]

'/sbin/mdadm --examine --scan --config=partitions' hangs. This can be trivially reproduced when updating a kernel or updating the initramfs, or just running the program directly.

Relevant excerpt from stracing the process:

[...]
getdents(4, /* 0 entries */, 65536) = 0
close(4) = 0
read(3, "", 1024) = 0
close(3) = 0
open("/dev/dm-9", O_RDONLY|O_DIRECT) = 3
fstat(3, {st_mode=S_IFBLK|0660, st_rdev=makedev(252, 9), ...}) = 0
ioctl(3, RAID_VERSION

/dev/dm-9 on this system is "mpathg", a standard disk claimed by multipathd. I cannot find anything relevant to this ioctl in multipath itself.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.4.0-72-generic 4.4.0-72.93
ProcVersionSignature: Ubuntu 4.4.0-72.93-generic 4.4.49
Uname: Linux 4.4.0-72-generic ppc64le
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
AlsaDevices:
 total 0
 crw-rw---- 1 root audio 116, 1 Apr 11 18:34 seq
 crw-rw---- 1 root audio 116, 33 Apr 11 18:34 timer
AplayDevices: Error: [Errno 2] No such file or directory: 'aplay'
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: ppc64el
ArecordDevices: Error: [Errno 2] No such file or directory: 'arecord'
AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
Date: Mon Jun 12 20:23:08 2017
IwConfig: Error: [Errno 2] No such file or directory: 'iwconfig'
Lsusb:
 Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
PciMultimedia:

ProcFB:

ProcKernelCmdLine: root=/dev/mapper/mpath0-part2 ro console=hvc0
ProcLoadAvg: 0.73 0.72 0.93 2/3127 150908
ProcSwaps:
 Filename Type Size Used Priority
 /swap.img file 8388544 0 -1
ProcVersion: Linux version 4.4.0-72-generic (buildd@bos01-ppc64el-022) (gcc version 5.4.0 20160609 (Ubuntu/IBM 5.4.0-6ubuntu1~16.04.4) ) #93-Ubuntu SMP Fri Mar 31 14:05:15 UTC 2017
RelatedPackageVersions:
 linux-restricted-modules-4.4.0-72-generic N/A
 linux-backports-modules-4.4.0-72-generic N/A
 linux-firmware 1.157.8
RfKill: Error: [Errno 2] No such file or directory: 'rfkill'
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
cpu_cores: Number of cores present = 20
cpu_coreson: Number of cores online = 20
cpu_dscr: DSCR is 0
cpu_freq:
 min: 3.691 GHz (cpu 152)
 max: 3.691 GHz (cpu 8)
 avg: 3.691 GHz
cpu_runmode:
 Could not retrieve current diagnostics mode,
 No kernel interface to firmware
cpu_smt: SMT is off

[Joseph Salisbury (jsalisbury)]

This change was made by a bot.

[Joseph Salisbury (jsalisbury)]

Did this issue start happening after an update/upgrade? Was there a prior kernel version where you were not having this particular problem?

Would it be possible for you to test the latest upstream kernel? Refer to https://wiki.ubuntu.com/KernelMainlineBuilds . Please test the latest v4.12 kernel[0].

If this bug is fixed in the mainline kernel, please add the following tag 'kernel-fixed-upstream'.

If the mainline kernel does not fix this bug, please add the tag: 'kernel-bug-exists-upstream'.

Once testing of the upstream kernel is complete, please mark this bug as "Confirmed".

Thanks in advance.

[0] http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.12-rc5

[Dimitri John Ledkov (xnox)]

Current kernel is 4.4.0-97-generic given we are blocked generating initramfs, upgrading kernels is interesting...

We do not have any mdadm raids on this system, so I will try removing mdadm; upgrading kernels; re-installing mdadm to reproduce the issue.