Comment 21 for bug 345714

Thanks for the backtrace Robbie, that helps pinpoint where things are failing. The failure seems to be happening in the kernel itself. The last point it is in X-land is with this stanza of code:

    case ACTION_SWITCHSCREEN_PREV:
        if (VTSwitchEnabled && !xf86Info.dontVTSwitch && xf86Info.vtno > 0) {
            if (ioctl(xf86Info.consoleFd, VT_ACTIVATE, xf86Info.vtno - 1) < 0)
                ErrorF("Failed to switch consoles (%s)\n", strerror(errno));
        }
        break;

The ioctl calls into the kernel from there, but we have no further debug info as to what it's doing there:

#0 0xb7fdc424 in __kernel_vsyscall ()
No symbol table info available.
#1 0xb7c6ad59 in ioctl () from /lib/tls/i686/cmov/libc.so.6
No locals.

Some things I can rule _out_:

1. "*ERROR* trying to get vblank count" - it sounds bad, but is a common warning unrelated to this issue

2. In the second backtrace there is a "*** glibc detected ***" bit - I think this portion of the crash is actually just bug #328035 (which was causing a lot of glibc X failures all over the place). It is now fixed (post-beta) in xorg-server (2:1.6.0-0ubuntu5)

3. The crash on switching user is a different bug not related to this.