Re: [uml-devel] [uml-user] Hanging using 'iptables -L' in UML vm booted with con0=pts

[Blaisorblade <blaisorblade@yahoo.it>]

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On giovedì 13 settembre 2007, Fermín Galán Márquez wrote:
> Dear Jeff,
>
> Jeff Dike wrote:
> > On Wed, Sep 12, 2007 at 11:52:32PM +0200, Fermín Galán Márquez wrote:
> >> This is the trace (as you can see I're repeated the experiment twice,
> >> the result is basically the same), hoping it could be useful to diagnose
> >> the problem and fix eventual bugs in the UML kernel. See below regarding
> >> the test procedure.
> >>
> >> (gdb) bt
> >> #0  0xb7f9d7f2 in ?? () from /lib/ld-linux.so.2
> >> #1  0xb7f19ab0 in tcsetattr () from /lib/i686/cmov/libc.so.6
> >> #2  0x080610d5 in generic_console_write (fd=7,
> >>     buf=0x828fc13 "ip_tables: (C) 2000-2006 Netfilter Core Team\n",
> >> n=45) at arch/um/drivers/chan_user.c:37
> >> #3  0x0806096e in console_write_chan (chans=0x82756f0,
> >>     buf=0x828fc13 "ip_tables: (C) 2000-2006 Netfilter Core Team\n",
> >> len=45) at arch/um/drivers/chan_kern.c:352
> >
> > Are you capturing UML output with a script or something?  This is the
> > signature of the script not reading from the pty, so everything just
> > backs up, waiting for the pty to clear up.
>
> AFAIK, no script is capturing (I understand you refers to the output of
> the UML linux executable) and, as a matter of fact, I'm getting some
> output when execute ./linux. To be precise, this is the exact command
> (and the output) I get:
>
> cibeles:/tmp# ./linux ubd0=/tmp/root_fs_debug con=null con0=pts
> uml_dir=/tmp umid=run
> Core dump limits :
>          soft - 0
>          hard - NONE
> Checking that ptrace can change system call numbers...OK
> Checking syscall emulation patch for ptrace...OK
> Checking advanced syscall emulation patch for ptrace...OK
> Checking for tmpfs mount on /dev/shm...OK
> Checking PROT_EXEC mmap in /dev/shm/...OK
> Checking for the skas3 patch in the host:
>    - /proc/mm...not found: No such file or directory
>    - PTRACE_FAULTINFO...not found
>    - PTRACE_LDT...not found
> UML running in SKAS0 mode
> [no more output, no new prompt]
>
> Then, in a second terminal in the host, I get the pts device and open a
> screen in the vm:
>
> cibeles:/tmp# uml_mconsole run/mconsole config con0
> Warning: couldn't stat file: /root/.uml/run/mconsole/mconsole - No such
> file or directory
> Warning: couldn't stat file: /tmp/uml/run/mconsole/mconsole - No such
> file or directory
> OK pts:/dev/pts/1
> cibeles:/tmp# screen /dev/pts/1
> [the terminal "goes into" the vm. I use it to cause the fail, as seen
> below] Debian GNU/Linux lenny/sid vm tty0
>
> vm login: root
> Password:
> Last login: Wed Sep 12 23:32:36 2007 on tty0
> Linux vm 2.6.22.4-xt-2m #1 Wed Sep 12 20:24:20 CEST 2007 i686
>
> The programs included with the Debian GNU/Linux system are free software;
> the exact distribution terms for each program are described in the
> individual files in /usr/share/doc/*/copyright.
>
> Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
> permitted by applicable law.
> vm:~# iptables -L
> [no output, linux process reach 100% CPU usage in the host]
>
> In a third host terminal I run gdb:
>
> cibeles:/tmp# cat run/pid
> 6627
> cibeles:/tmp# gdb ./linux 6627
>
> GNU gdb 6.4.90-debian
> Copyright (C) 2006 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you
> are welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "i486-linux-gnu"...Using host libthread_db
> library "/lib/i686/cmov/libthread_db.so.1".
>
> Attaching to program: /tmp/linux, process 6627
> Reading symbols from /lib/i686/cmov/libutil.so.1...done.
> Loaded symbols for /lib/i686/cmov/libutil.so.1
> Reading symbols from /lib/i686/cmov/libc.so.6...done.
> Loaded symbols for /lib/i686/cmov/libc.so.6
> Reading symbols from /lib/ld-linux.so.2...done.
> Loaded symbols for /lib/ld-linux.so.2
> 0xb7f947f2 in ?? () from /lib/ld-linux.so.2
> (gdb) bt
> [showing the trace I've already sent in the other mail]
>
> Maybe there are "other outputs" apart of the output that the ./linux
> produces which could be causing the problem?

Please try logging in via SSH and reproducing the problem and the stacktrace, 
and also removing con=null - also have you double checked con=null is ok 
(maybe it was con=none, I'm not sure). I'm not sure screen is perfectly safe 
to use (it should be).
-- 
"Doh!" (cit.), I've made another mistake!
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729
http://www.user-mode-linux.org/~blaisorblade

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