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swedish

Member

Registered: 2015-07-09

Posts: 5

[solved] lightdm crashes after update, in _dl_relocate_object

After a few weeks away, I came home and decided to update my system. The update seemed to run fine so I rebooted, but lightdm never came up. Log files show that it crashes, in _dl_relocate_object (ld-linux-x86-64.so.2)

Dec 15 12:17:20 mythbox systemd-coredump[270]: Process 259 (lightdm) of user 0 dumped core.
                                               
                                               Stack trace of thread 259:
                                               #0  0x00007f64c4ad7511 _dl_relocate_object (ld-linux-x86-64.so.2)
                                               #1  0x00007f64c4acff23 dl_main (ld-linux-x86-64.so.2)
                                               #2  0x00007f64c4ae2e00 _dl_sysdep_start (ld-linux-x86-64.so.2)
                                               #3  0x00007f64c4ad0d8a _dl_start (ld-linux-x86-64.so.2)
                                               #4  0x00007f64c4accd88 _start (ld-linux-x86-64.so.2)

At first, it appeared to be similar to the issue in https://bbs.archlinux.org/viewtopic.php?id=203223. At least, both gdk-pixbuf-query-loaders and gtk-query-immodules-3.0 also throw a segmentation fault. However, I'm running a Core2Duo E6300, which is definitely not a new CPU. I also don't have any nvidia hardware installed, nor any nvidia software installed. Also I'm not getting the segfault in __lll_unlock_elision but in _dl_relocate_object.

So far I have tried:
Reinstalling lightdm + glibc
Installing extra/intel-ucode-20150121 (changed microcode version from 0xa07 to 0xa0b)
Manually upgrading intel-ucode to 20151106 (same resulting versions as 20150121).
Numerous reboots.

I'm not sure where to go next. I can't believe that I'm the only person who runs lightdm, so I don't think it's any particular bug in lightdm. However lightdm is also crashing fast enough that it never even opens up a new logfile.

Last edited by swedish (2015-12-15 09:02:08)

swedish

Member

Registered: 2015-07-09

Posts: 5

Re: [solved] lightdm crashes after update, in _dl_relocate_object

Resolved. Somehow the system was in some completely messed up state. glib2 was installed, but partially not-installed. No idea how it got there, seeing as the recent update appeared to run fine. Reinstalled glib2 and system appears functional so far.

Details:

Checked an actual backtrace, saw g_module_open() from libgmodule in the stack. However, when I checked, no package claimed ownership of libgmodule* which had me intrigued. I tried to reinstall glib2, but despite warning about reinstalling, it failed due to pre-existing files in the filesystem.

# pacman -S glib2
warning: glib2-2.46.2-2 is up to date -- reinstalling
resolving dependencies...
looking for conflicting packages...

Packages (1) glib2-2.46.2-2

Total Installed Size:  12.60 MiB

:: Proceed with installation? [Y/n] y
(1/1) checking keys in keyring                                                                                    [####################################################################] 100%
(1/1) checking package integrity                                                                                  [####################################################################] 100%
(1/1) loading package files                                                                                       [####################################################################] 100%
(1/1) checking for file conflicts                                                                                 [####################################################################] 100%
error: failed to commit transaction (conflicting files)
glib2: /usr/bin/gapplication exists in filesystem
glib2: /usr/bin/gdbus exists in filesystem
glib2: /usr/bin/gdbus-codegen exists in filesystem
glib2: /usr/bin/gio-querymodules exists in filesystem

I've left out many lines here. I tried again with --force, the install ran fine, and it seems everything works once again. No idea how the system got into this state. My guess is somehow an update installed some of the files (but not all, or not completely?) but never marked them in the database as installed. I figure I'd leave this here as an indicator that if there's a segfault in _dl_relocate_object, it's worth looking higher (lower?) in the stack for other culprits.