AC97 sound card crashes QEMU

The AC97 sound card does not work. It stops QEMU on startup. The cause appears to be some kind of deadlock. 

Steps to reproduce:
Just add -soundhw ac97 to QEMU's arguments. Example: qemu-system-ppc -soundhw ac97

The example above is all it takes to reproduce the problem.

This problem has been observed on Mac OS X and Debian Linux. 

I question whether the ac97 support ever worked. It is a file that was taken from VirtualBox and added to QEMU. I do know that VirtualBox's support for the ac97 sound card works perfectly. 

The exact line of code that stops QEMU in its tracks is located in the file main-loop.c, in the function os_host_main_loop_wait(), the call made to qemu_mutex_lock_iothread(). The is where QEMU stops under Mac OS X.