[Pkg-uml-pkgs] Bug#701886: user-mode-linux: traced processes freeze after 26-Feb-2013 update

[Mihail Groza]

Package: user-mode-linux
Version: 2.6.32-1um-4+48squeeze1
Severity: normal


When trying to trace running processes (either strace or gdb), programs
freeze.

As an example:

    $ cat test.c
    #include <stdio.h>
    int
    main(void)
    {
        fprintf(stdout, "Hello, World!\n");
        return 0;
    }
    $ gcc -g -o test test.c
    $ strace ./test

gives the following warning:

    ------------[ cut here ]------------
    WARNING: at kernel/sched.c:2628 wake_up_process+0x34/0x40()
    Modules linked in: ipv6 binfmt_misc
    48fa3e94:  [<0809c7b0>] warn_slowpath_common+0x60/0x90
    48fa3ea4:  [<080996d4>] wake_up_process+0x34/0x40
    48fa3eb8:  [<080996d4>] wake_up_process+0x34/0x40
    48fa3ecc:  [<080601c5>] arch_ptrace+0x155/0x360
    48fa3ee4:  [<080af7e7>] find_task_by_pid_ns+0x17/0x40
    48fa3eec:  [<080a6629>] ptrace_check_attach+0x69/0x90
    48fa3f00:  [<080a6a3f>] sys_ptrace+0x7f/0x150
    48fa3f24:  [<08062c0b>] handle_syscall+0xbb/0xc0
    48fa3f40:  [<080a69c0>] sys_ptrace+0x0/0x150
    48fa3f6c:  [<080915e2>] userspace+0x3a2/0x560
    48fa3fec:  [<0805fcad>] fork_handler+0x5d/0x70

    ---[ end trace d636ea18fe67c05f ]---

and the process freezes. The same behaviour can be observed when using
gdb (this is how I found it).

Rolled back to previous version (2.6.32-1um-4+45) and tested the same
test program -- the incorrect behaviour is no longer observed.

-- System Information:
Debian Release: 6.0.7
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-5-686 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages user-mode-linux depends on:
ii  libc6                       2.11.3-4     Embedded GNU C Library: Shared lib
ii  uml-utilities               20070815-1.1 User-mode Linux (utility programs)

user-mode-linux recommends no packages.

Versions of packages user-mode-linux suggests:
ii  gnome-terminal [x-terminal-em 2.30.2-1   The GNOME terminal emulator applic
pn  rootstrap                     <none>     (no description available)
pn  slirp                         <none>     (no description available)
pn  user-mode-linux-doc           <none>     (no description available)
pn  vde2                          <none>     (no description available)

-- no debconf information