After a hard lockup and reboot, my test box (running recent Linus git
851b147) came up with:

[    5.016854] EXT4-fs (sda1): mounted filesystem with ordered data mode
[    8.809125] EXT4-fs (sda1): internal journal on sda1:8
[   10.165239] EXT4-fs error (device sda1): ext4_lookup: deleted inode referenced: 524788
[   10.165286] Aborting journal on device sda1:8.
[   10.168111] EXT4-fs error (device sda1): ext4_journal_start_sb: Detected aborted journal
[   10.168169] EXT4-fs (sda1): Remounting filesystem read-only
[   10.171614] EXT4-fs (sda1): Remounting filesystem read-only

Complete dmesg and kconfig attached.  The lockup was running the same
kernel and X with a kernel "make -j4" on sda1 and a "dd if=/dev/zero
bs=1M of=/dev/sdb1" to a USB thumb drive running simultaneously; I'd
Ctrl-C'ed the dd about 30 seconds before the machine locked up (and the
dd was still in "D" so I'd attached an strace to it to see if anything
interesting would happen when it finally came back).

I haven't rebooted or remounted RW yet, happy to run whatever debug
commands would be useful.

Two issues here:

1. the lockup sucks, but I have no idea what to do about it.  There's
nothing useful in the logs and it wasn't responding to SysRq and the
keyboard LEDs weren't blinking.

2. after a lockup the journal recovery should not fail.

-andy