ata panic: "mtx_lock of destroyed mutex"

[Matthew Jacob]

Hmm. I just fixed that at Panasas, and I'm pretty sure that I gave the 
patch to Alexander Motin to put in.

> I've been setting up an amd64 VirtualBox machine with the latest
> 9-CURRENT and got the following panic when booting it (another machine
> updated and booting at the same time didn't panic):
>
> ata1: WARNING - READ_TOC read data overrun 18>12
> panic: mtx_lock of destroyed mutex @ /usr/src/sys/kern/kern_sema.c:79
> cpuid = 0
>
> with the following stack trace:
>
> kdb_enter
> panic
> _mtx_lock_flags
> _sema_post
> ata_completed
> taskqueue_run
> intr_event_execute_handlers
> ithread_loop
> fork_exit
> fork_trampoline
>
>