[Pkg-uml-pkgs] Bug#544225: a fresh Debian Squeeze system hangs while booting under UML

[Ivan Shmakov]

Package: user-mode-linux
Version: 2.6.26-1um-2+17lenny2

	A freshly-installed Debian Squeeze system seems to hang at early
	stages of the boot process when run under UML:

VFS: Mounted root (ext3 filesystem) readonly.
INIT: version 2.86 booting
Starting the hotplug events dispatcher: udevd.
Synthesizing the initial hotplug events...[... Hangs indefinitely here...]

	Should, however, the `udev' script be excluded from the boot
	sequence, e. g., by entering the ``emergency mode'', and then:

(none):~# e2fsck /dev/ubda 
e2fsck 1.41.3 (12-Oct-2008)
/dev/ubda: clean, 12230/262144 files, 114329/1048576 blocks
(none):~# mount -o remount,rw / 
EXT3 FS on ubda, internal journal
(none):~# mv -vi /etc/rcS.d/S{,.}03udev 
`/etc/rcS.d/S03udev' -> `/etc/rcS.d/S.03udev'
(none):~# mount -o remount,ro / 
(none):~# exit 

	the system seems to boot just fine.

	Running `strace -p' on an active (100% CPU) thread during the
	hang gives the following output (fragments):

...
munmap(0x78b06000, 4096)                = 0
mmap(0x78b06000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d32000) = 0x78b06000
munmap(0x78b07000, 4096)                = 0
mmap(0x78b07000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d33000) = 0x78b07000
munmap(0x78b08000, 4096)                = 0
mmap(0x78b08000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d34000) = 0x78b08000
munmap(0x78b09000, 4096)                = 0
munmap(0x78b0a000, 4096)                = 0
munmap(0x78b0b000, 4096)                = 0
...
munmap(0x78bfd000, 4096)                = 0
munmap(0x78bfe000, 4096)                = 0
munmap(0x78bff000, 4096)                = 0
rt_sigreturn(0)                         = 1048816
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
munmap(0x78800000, 4096)                = 0
mmap(0x78800000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821a000) = 0x78800000
munmap(0x78801000, 4096)                = 0
mmap(0x78801000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821b000) = 0x78801000
munmap(0x78802000, 4096)                = 0
mmap(0x78802000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821c000) = 0x78802000
...
munmap(0x78b06000, 4096)                = 0
mmap(0x78b06000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d32000) = 0x78b06000
munmap(0x78b07000, 4096)                = 0
mmap(0x78b07000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d33000) = 0x78b07000
munmap(0x78b08000, 4096)                = 0
mmap(0x78b08000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x16d34000) = 0x78b08000
munmap(0x78b09000, 4096)                = 0
munmap(0x78b0a000, 4096)                = 0
munmap(0x78b0b000, 4096)                = 0
munmap(0x78bfd000, 4096)                = 0
munmap(0x78bfe000, 4096)                = 0
munmap(0x78bff000, 4096)                = 0
rt_sigreturn(0)                         = 1048816
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
munmap(0x78800000, 4096)                = 0
mmap(0x78800000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821a000) = 0x78800000
munmap(0x78801000, 4096)                = 0
mmap(0x78801000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821b000) = 0x78801000
munmap(0x78802000, 4096)                = 0
mmap(0x78802000, 4096, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_SHARED|MAP_FIXED, 3, 0x1821c000) = 0x78802000
...

	The child system image was prepared with rootstrap(1):

$ cat rootstrap.conf 
[global]
fstype = ext3
initialsize = 4096
umlargs = mem=256M

[network]
hostname = rootstrap-2009-08-29
interface = eth0
transport = slirp
host =
uml = 10.0.2.15
nameserver = 10.0.2.3
gateway = 10.0.2.2
netmask = 255.255.0.0
slirp = slirp-fullbolt

[debian]
dist = squeeze
mirror = [...]
install = bash bind9-host bzip2 less lzma openssh-client openssh-server psmisc time tree zip
$ 

	UML was started like:

$ LC_ALL=C script -c \
      '/usr/bin/time linux.uml con0=fd:0,fd:1 con=pts \
           eth0=slirp,,slirp-fullbolt \
           root=/dev/ubda ubd0=2009-08-29.cow \
           mem=256M umid=2009-08-29.cow jail mem=384M' 

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