The little script attached in this email manages to crash my fossil server with 100% reproducibility (i.e. 5 out of 5, I got sick of rebooting so I'm not trying anymore). The error message on the console is: [heavy io] disk: io=10000 at 0.991ms assert failed: b->nlock == 1 fossil 44: suicide: sys: trap: fault read addr=0x0 pc=0x0002b5af [here I usually reboot] The machine does not panic, it simply becomes unusable. The attachment: the attached archive includes a small program that I use to extract subfonts from a .bdf font file. It's a modified version of Skip Tavakkolian's bdf2subf. Also included is a sample .bdf file. The script 'runtest' will extract all glyphs from the .bdf file and save them in files named according to the range the subfont covers; after the extraction is complete the script will attempt to detele all subfont files and will cause my fossil to crash. Symptoms: I don't seem to lose any other data. Before deletion there are 5000+ files in the directory. After a reboot I usually find around 1600 still remaining. Setup: I run fossil over a two-disk mirror using devfs, the disks it mirrors to are 80GB Matrox IDE disks set up as sdC0 and sdD0, running with UDMA4. Debugging: Had a brief look at /sys/src/cmd/fossil/cache.c (where the nlock mangling occurs, the assert fails in disk.c) but the code looks like it's in a working state still -- so here's reporting the error to those who know how to fix it better than I do. cheers, andrey