Hi Ubuntu users!  Signal 7 is SIGBUS.  SIGBUS should be relatively
unusual on x86 [1].

[1] https://stackoverflow.com/questions/2089167/debugging-sigbus-

I'm excited to inform you that Fedora Linux users also started seeing
the same root problem.  It is tied to the upgrade from kernel v4.14 to

Fedora bug report:

Arch Linux independently identified this as caused by the kernel upgrade:

It can happen after resume from suspend, not every time but maybe once
every three days.  We have reports for both Xwayland and Xorg getting a
fatal SIGBUS in _dl_fixup().  (While this is actually a secondary crash
in xorg_backtrace(), we have a load of SIGBUS traces that have the same
primary trace as each other).

Notice the specific faulting instruction in disassembly you captured: it
is not performing a memory access!

=> 0x559c102a4060 <ErrorFSigSafe>:      sub    $0xd8,%rsp

Instead, notice that this is the first instruction in the function
ErrorFSigSafe.  This is a big common factor in our traces.  (We actually
have several different traces captured, with the failing function
varying, often along the same call chain).

What's happening is a fault on the instruction fetch.  You should be
able to confirm this if you look at the address which generates the
fault.  (si_addr field of struct siginfo.  I don't know where the Ubuntu
crash collector saves this information)

The kernel failed to load in the page which holds the program code at
this point.  That's the real problem: some sort of transient IO error
during wakeup.  Users sometimes see other symptoms of these IO errors as

PM: resume devices took 1.017 seconds
Restarting tasks ...
Read-error on swap-device (253:1:836184)
PM: suspend exit
systemd-coredump[755]: Process 1356 (Xwayland) of user 42 dumped core.


PM: suspend exit
EXT4-fs error (device dm-2): ext4_find_entry:1436: inode #5514052: comm 
thunderbird: reading directory lblock 0
Buffer I/O error on dev dm-2, logical block 0, lost sync page write
WARNING: CPU: 1 PID: 748 at fs/buffer.c:1108 mark_buffer_dirty+0xd4/0xe0
 (and a kernel backtrace)

** Bug watch added: Red Hat Bugzilla #1553979

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  Xorg crashed with signal 7 in _dl_fixup()

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