DragonFly bugs List (threaded) for 2004-01
Re: kldunload Ratal trap 12: page fault
Ok, I found it. Here is the dependancy:
snd_sb16 depends on snd_pcm and snd_sbc
snd_sbc depends on snd_pcm
The problem is that snd_sbc is not bumping the ref count on snd_pcm.
If you attempt to kldload snd_sbc manually, with no other sound modules
loaded, it will fail trying to find a symbol. It will not load snd_pcm.
When you try to load snd_sb16, it forces snd_sbc and snd_pcm to be loaded.
But when you unload snd_sb16, since there is no information on the
sbc->pcm dependancy, snd_sb16 will happily unload snd_pcm BEFORE
The fix is to add the appropriate KMODDEPS to the Makefile for sbc
(/usr/src/sys/dev/sound/driver/sbc/Makefile), which I just did.
Ok, so what about the MODULE_DEPEND() lines in the module source code?
We implement the proper linker sets to support MODULE_DPEND(), but we
do not yet implement code to actually use them. FreeBSD-5, but it's
a terrible hack.
What needs to be done in DragonFly is to (A) load the modules associated
with MODULE_DEPEND() linker sets in the kld, (B) restrict the
dynamic linking symbol lookups to just those symbols available from the
kernel and specified MODULE_DEPEND() lines, and (C) remove the global
symbol data and make it per-module like it should have been in the first
FreeBSD-5 does (A) but does not do (B) or (C) (as far as I can tell).