(I couldn't find a kernel bugzilla component for LXC bugs, so I picked something that sounded vaguely related.)

gdb is unable to debug bash once the command "ls" is typed in, but only inside an LXC container (outside the container, it works). The error message from gdb is:

Couldn't write debug register: No such process

Steps to Reproduce:
1. Set up an LXC chroot containing gdb and bash (on Fedora Linux, this can be done fairly easily by installing and configuring mach and then using "mach yum install gdb bash". mach also supports apt-get.) I also installed the separate -debuginfo packages inside the container, but I don't think this matters.
2. I use the libvirt command-line tools to actually start the LXC container, because I couldn't manage to get the LXC userspace tools to create a container. Define the LXC chroot in virsh, e.g. virsh define foo.xml for some libvirt
configuration file foo.xml
3. virsh --connect lxc:/// start foo && virsh --connect lxc:/// console foo
4. export PATH=/usr/bin:$PATH
5. gdb /bin/bash
6. Type 'r' to run bash
7. Inside that bash process, type 'ls' and hit the enter key

At this point it says 
Couldn't write debug register: No such process

FYI, I get a slightly different error message if I use the Fedora kernel instead of the mainline kernel:
Waiting for child: no such process

Regarding the regression flag: I am *guessing* this is a regression, because the very similar bug that I just mentioned in the Fedora kernel tree is definitely a regression. I plan to test older and newer mainline kernel versions at a later date.