2 bonnies can stop disk activity permanently

[Scott Long]

Kris Kennaway wrote:

> On Sun, Oct 08, 2006 at 08:22:13AM -0700, R. B. Riddick wrote:
> 
>>Hi!
>>
>>We (me and Veronica) mentioned, that starting 2 bonnie (ports/bench) processes on a UFS
>>1. on a geom_bsd, geom_disk (like ad4 or da0) and geom_stripe (using ad4a, ..., ad10a)
>>2. with different controllers areca and nVidia and different motherboards and
>>3. with up to 8 SATA disks
>>results in a permanently disk-dead system.
>>
>>
>>Veronica's box had more than 700MB of free memory (according to top), when it happened.
>>
>>Heavy load (caused by blogbench, rawio, raidtest and dd) causes no problem, while bonnie gets stuck somewhere between putc phase and end of rewrite phase.
>>
>>The bonnie processes were blocked due to "nbufkv" (some VFS reason).
>>Geom activity is impossible then (no file system activity happens).
>>No syslog message can be seen on the console.
> 
> 
> You forgot to even mention what version you're running ;-)
> 
> Also show your kernel config file.  Configure DDB per the chapter on
> kernel debugging in the developers handbook, break to DDB from the
> console or serial console, then show us what processes are running and
> what are their backtraces.
> 
> Kris

No need for all of that information, the bug in vfs_bio.c is quite 
obvious. =-(  Fixing it will take some thought, though.

Scott