This is what's happening: 1 - boot UML using root_fs 2 - shutdown UML - doesn't shutdown properly, leaving root_fs open and locked 3 - boot UML again 4 - new UML cannot use root_fs due to lock held by old UML
I am seeing this problem on my setup. "shutdown" on a UML does not
terminate. It gets to the "power down" point but the /usr/bin/linux
process does not exit, rather it hangs forever. If I hit ^C then
I get a shell prompt back, but there is still a [linux] process
which cannot be killed.
This is 2.4.26-3um running on host 2.6.10 with the skas3-v8 patch.
Observe:
baron:~# ps axuww | grep linux
usermode 954 0.0 0.0 304 300 ? T Apr29 1:15 [linux]
usermode 24870 0.0 0.4 262232 8620 ? T 18:32 0:00 linux
con0=fd:0,fd:1 mem=256m
eth0=tuntap,,,10.1.0.1ubd0=linux-mantis.image
usermode 24991 0.9 3.2 262248 67180 pts/4 S+ 18:38 0:11 linux [depmod]
con0=fd:0,fd:1 mem=256m
eth0=tuntap,,,10.1.0.1ubd0=linux-mantis.image
usermode 24994 0.2 0.1 16392 2124 pts/4 T+ 18:38 0:03 [linux]
usermode 25003 0.0 3.2 262248 67180 pts/4 S+ 18:38 0:00 linux [depmod]
con0=fd:0,fd:1 mem=256m
eth0=tuntap,,,10.1.0.1ubd0=linux-mantis.image
usermode 25004 0.0 3.2 262248 67180 pts/4 S+ 18:38 0:00 linux [depmod]
con0=fd:0,fd:1 mem=256m
eth0=tuntap,,,10.1.0.1ubd0=linux-mantis.image
usermode 25005 0.0 3.2 262248 67180 pts/4 S+ 18:38 0:00 linux [depmod]
con0=fd:0,fd:1 mem=256m
eth0=tuntap,,,10.1.0.1ubd0=linux-mantis.image
The last 4 processes are a working UML instance. The first two are old UMLs
which did not shutdown or startup correctly.
Status 'T' means "traced or stopped". Not a zombie, so it should be killable.
baron:~# ls -l /proc/954/fd
total 20
lrwx------ 1 root root 64 May 5 18:59 0 -> /dev/pts/0 (deleted)
lrwx------ 1 root root 64 May 5 18:59 1 -> /dev/pts/0 (deleted)
lrwx------ 1 root root 64 May 5 18:59 10 -> socket:[2912]
lrwx------ 1 root root 64 May 5 18:59 11 -> socket:[2913]
lrwx------ 1 root root 64 May 5 18:59 12 -> socket:[2914]
lrwx------ 1 root root 64 May 5 18:59 13 ->
/baron/FileSystems/linux-mantis.image (deleted)
l-wx------ 1 root root 64 May 5 18:59 14 -> /proc/mm
l-wx------ 1 root root 64 May 5 18:59 15 -> /proc/mm
l-wx------ 1 root root 64 May 5 18:59 16 -> /proc/mm
l-wx------ 1 root root 64 May 5 18:59 17 -> /proc/mm
lr-x------ 1 root root 64 May 5 18:59 18 -> /baron/.uml/wnTBF0 (deleted)
lrwx------ 1 root root 64 May 5 18:59 19 -> socket:[2924]
lrwx------ 1 root root 64 May 5 18:59 2 -> /dev/pts/0 (deleted)
lrwx------ 1 root root 64 May 5 18:59 3 -> /tmp/vm_file-iUsEEz (deleted)
lrwx------ 1 root root 64 May 5 18:59 4 -> socket:[2905]
lrwx------ 1 root root 64 May 5 18:59 5 -> socket:[2906]
lrwx------ 1 root root 64 May 5 18:59 6 -> socket:[2907]
lrwx------ 1 root root 64 May 5 18:59 7 -> socket:[2909]
lrwx------ 1 root root 64 May 5 18:59 8 -> socket:[2910]
lrwx------ 1 root root 64 May 5 18:59 9 -> socket:[2911]
I had to copy the filesystem image to another file and rename it
over the top of the original before I could run UML again.
baron:~# kill -9 954
baron:~# kill -9 954
baron:~# kill -9 954
baron:~# kill -9 954
baron:~# kill -9 24870
baron:~# kill -9 24870
baron:~# kill -9 24870
baron:~# kill -9 24870
baron:~# ps uww 954
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
usermode 954 0.0 0.0 304 300 ? T Apr29 1:15 [linux]
These processes cannot be killed.
But I just found that I can do this:
baron:~# kill -CONT 954
baron:~# kill -9 954
-bash: kill: (954) - No such process
baron:~# kill -CONT 24870
baron:~# ps uww 24860
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
So sending them a SIGCONT gets the process going again. That leaves
the questions: why did the shutdown hang in the first place, is the
process SIGSTOPing itself, and if I had done a "kill -CONT" before
doing a "kill -9" would the process have exited cleanly?
Nick.
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