Bug#624263: grub-pc: stuck in grub-mkdevicemap at configure time

[Yann Dirson]

On Wed, Apr 27, 2011 at 09:27:25AM +0100, Colin Watson wrote:
> On Wed, Apr 27, 2011 at 12:52:44AM +0200, Yann Dirson wrote:
> > [UPGRADE] grub-pc 1.98+20100804-14 -> 1.99~rc1-13
> > 
> > When upgrading, aptitude gets stuck with:
> > 
> > Setting up grub-pc (1.99~rc1-13) ...
> > Installing new version of config file /etc/grub.d/05_debian_theme ...
> > Replacing config file /etc/default/grub with new version
> > 
> > $ pstree -alp 6275
> > grub-pc.postins,6275 /var/lib/dpkg/info/grub-pc.postinst configure 1.98+20100804-14
> >   ├─grep,6277 -v ^(fd[0-9]\\+)
> >   └─grub-mkdevicema,6276 -m -
> > 
> > $ ps l 6275  6277 6276
> > F   UID   PID  PPID PRI  NI    VSZ   RSS WCHAN  STAT TTY        TIME COMMAND
> > 1     0  6275  6180  20   0  10884   752 wait   S+   pts/5      0:00 /bin/bash /var/lib/dpkg/info/grub-pc.postinst configure 1.98+20100804-14
> > 0     0  6276  6275  20   0  18288   928 blkdev D+   pts/5      0:00 grub-mkdevicemap -m -
> > 0     0  6277  6275  20   0   7592   572 pipe_w S+   pts/5      0:00 grep -v ^(fd[0-9]\+)
> > 
> > $ ps -o pid,wchan=WIDE-WCHAN-COLUMN -o comm 6276
> >   PID WIDE-WCHAN-COLUMN COMMAND
> >  6276 blkdev_get        grub-mkdevicema
> > 
> > 
> > Nothing suspect from dmesg - any idea how to quickly get more precise
> > info ?  Not sure I can get out of this to retry except by rebooting,
> > which would be quite a shame...
> 
> It may be difficult retrospectively.  Can you attach strace to find out
> what system call it's stuck in, and attach gdb (you may need to build
> grub2 locally for symbols) to get a backtrace?

Unfortunately, neither can complete attaching to the process, and I
even have to use kill -9 to get rid of strace and gdb afterwards.
Looks like I'd have to reboot and add the strace call to the postinst
before retrying ?

Bad bad bad :}

Maybe we can get some info from the kernel about the syscall details.
I have a couple of debugging features activated in this kernel (kgdb
notably), I could try to peek via this channel.

Other ideas ?