[uml-user] UML hang on shutdown

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I'm trying to build a UML guest system based on Gentoo and the 2.6.16.16
kernel.  It seems to work, except that it always hangs on shutdown at
the message " * Deactivating swap ...".  This is after syslog and sshd
have been shut down, so there's no log information and I can't get a ps
output.  My skills with gdb are limited (is it possible to get a
something like a ps listing from gdb or uml_mconsole?), but the UML
kernel seems to be spending some of its time in an idle loop and some in
the stack trace below.  I can kill the uml system with uml_mconsole, but
it's annoying to have to do that all the time.

Does anyone know why this is happening or how I can fix it?

Thanks,
Rennie deGraaf

Host kernel: 2.6.16-1.2096_FC4 (unmodified Fedora Core 4 kernel)
Host system: Fedora Core 4
Guest kernel: 2.6.16.16 (unmodified)
Guest system: Gentoo

Kernel stack trace:
Program received signal SIGINT, Interrupt.
sig_handler (sig=29) at arch/um/os-Linux/signal.c:42
42      in arch/um/os-Linux/signal.c
(gdb) bt
#0  sig_handler (sig=29) at arch/um/os-Linux/signal.c:42
#1  <signal handler called>
#2  0x002ed402 in __kernel_vsyscall ()
#3  0x003c7513 in __write_nocancel () from /lib/libc.so.6
#4  0x08083119 in file_io (fd=11, buf=0xa0b3adc, len=64, io_proc=0x805c440,
    copy_user_proc=0x805fe50 <copy_to_user_proc>)
    at arch/um/os-Linux/file.c:333
#5  0x0807f7ca in do_ubd_request (q=0x9502bc8)
    at arch/um/drivers/ubd_kern.c:1054
#6  0x0816641b in generic_unplug_device (q=0x9502bc8) at
block/ll_rw_blk.c:1611
#7  0x080d4a58 in swap_unplug_io_fn (unused_bdi=0x82644f8, page=Variable
"page" is not available.
)
    at include/linux/blkdev.h:629
#8  0x080e56e6 in block_sync_page (page=0x94a13a0)
    at include/linux/blkdev.h:629
#9  0x080bd562 in sync_page (word=0x94a13a0) at mm/filemap.c:165
#10 0x0820f225 in __wait_on_bit (wq=0x94b0600, q=0xa0b3b8c,
    action=0x80bd530 <sync_page>, mode=2) at kernel/wait.c:162
#11 0x080bdd51 in wait_on_page_bit (page=Variable "page" is not available.
) at mm/filemap.c:455
#12 0x080d5995 in try_to_unuse (type=0) at include/linux/pagemap.h:189
#13 0x080d6354 in sys_swapoff (specialfile=0x804f078 "\030\uffff\215\uffff")
    at mm/swapfile.c:1155
#14 0x080647ca in handle_syscall (r=0x96682d8)
    at arch/um/kernel/skas/syscall.c:42
#15 0x080897be in userspace (regs=0x96682d8)
    at arch/um/os-Linux/skas/process.c:151
#16 0x08064458 in fork_handler (sig=10)
    at arch/um/kernel/skas/process_kern.c:96
#17 <signal handler called>
#18 0x002ed402 in __kernel_vsyscall ()
#19 0x080890f4 in map (mm_idp=0xa8741bc, virt=32277, len=157712640,
r=3359623,
    w=1, x=1, phys_fd=6, offset=14423702927018972, done=1, data=0xa103aec)
    at arch/um/os-Linux/skas/mem.c:209
#20 0x0806495a in do_ops (mmu=0x94f8740, ops=0xa103ab8, last=136695296,
    finished=156206912, flush=0xa103aec) at arch/um/kernel/skas/tlb.c:31
#21 0x00000001 in ?? ()
#22 0x094f8740 in ?? ()
#23 0x0a103ab8 in ?? ()
#24 0x0825ce00 in init_sighand ()
#25 0x094f8740 in ?? ()
#26 0x0a100000 in ?? ()
#27 0x08089a99 in switch_threads (me=0x94f8c24, next=0x825baec)
    at arch/um/os-Linux/skas/process.c:485
#28 0x0806428d in switch_to_skas (prev=0x94f8740, next=0x825ce00)
    at arch/um/kernel/skas/process_kern.c:35
#29 0x0805f8fa in _switch_to (prev=0x333df7, next=0x825ce00, last=0x94f8740)
    at arch/um/kernel/process_kern.c:123
#30 0x0820e569 in schedule () at kernel/sched.c:1600
#31 0x0809aa57 in do_wait (pid=-1, options=4, infop=0x0,
stat_addr=0xbf501fc8,
    ru=0x0) at kernel/exit.c:1495
#32 0x0809ae61 in sys_wait4 (pid=-1, stat_addr=0xbf501fc8, options=0,
ru=0x0)
    at kernel/exit.c:1571
#33 0x0809ae95 in sys_waitpid (pid=-1, stat_addr=0xbf501fc8, options=0)
    at kernel/exit.c:1586
#34 0x080647ca in handle_syscall (r=0x94f8918)
    at arch/um/kernel/skas/syscall.c:42
#35 0x080897be in userspace (regs=0x94f8918)
    at arch/um/os-Linux/skas/process.c:151
#36 0x08064458 in fork_handler (sig=10)
    at arch/um/kernel/skas/process_kern.c:96
#37 <signal handler called>
#38 0x002ed402 in __kernel_vsyscall ()
#39 0x08089a99 in switch_threads (me=0x8e0db04, next=0xa0b3a34)
    at arch/um/os-Linux/skas/process.c:485
#40 0x0806428d in switch_to_skas (prev=0x8e0d620, next=0x9668100)
    at arch/um/kernel/skas/process_kern.c:35
#41 0x0805f8fa in _switch_to (prev=0x94f8bdc, next=0x9668100,
last=0x8e0d620)
    at arch/um/kernel/process_kern.c:123
#42 0x0820e569 in schedule () at kernel/sched.c:1600
#43 0x0820f113 in schedule_timeout (timeout=Variable "timeout" is not
available.) at kernel/timer.c:1136
#44 0x080f6ce5 in do_select (n=11, fds=0x8e13be0, timeout=0x8e13c38)
    at fs/select.c:276
#45 0x080f7007 in core_sys_select (n=11, inp=0xbf67f4d0, outp=0x0, exp=0x0,
    timeout=0x8e13c38) at fs/select.c:353
#46 0x080f715d in sys_select (n=11, inp=0xbf67f4d0, outp=0x0, exp=0x0,
    tvp=0xbf67f4c8) at fs/select.c:398
#47 0x080647ca in handle_syscall (r=0x8e0d7f8)
    at arch/um/kernel/skas/syscall.c:42
#48 0x080897be in userspace (regs=0x8e0d7f8)
    at arch/um/os-Linux/skas/process.c:151
#49 0x0806437f in new_thread_handler (sig=10)
    at arch/um/kernel/skas/process_kern.c:66
#50 <signal handler called>
#51 0x002ed402 in __kernel_vsyscall ()
#52 0x00000000 in ?? ()
(gdb)