svn commit: r224842 - head/sys/kern

[Robert Watson]

On Sun, 14 Aug 2011, Alexander Best wrote:

>> It might be worth mentioning this in UPDATING or similar, since a kernel 
>> built with clang (I haven't tried gcc) during this window will make it 
>> impossible to do a buildworld without first rebuilding the kernel with this 
>> fix. It also seems to break at least portsnap, and possibly other tools as 
>> well.
>
> +1. please also mention the KPI change to fget()! so many people have had 
> issues, where 3rd party drivers - mostly the nvidia binary driver - got 
> broken.

Now in place.  However, I think it's fairly likely that nVidia binary drivers 
will see further disruption in the future.  Other than preventing the driver 
from loading when it's out of sync with __FreeBSD_version (which I believe we 
now do?), I'm not sure what further is to be done there.  In general, we don't 
tweak things like fget(9) very often, but we do make changes to fileops with 
moderate frequency, and the failure modes there are quite a bit more subtle. 
It would be useful to see a KBI analysis of the nVidia module so we can decide 
how to moderate that risk.

(We've done some work on formalising the relationship between network device 
drivers and the kernel, which has led is to have specific policies on data 
structure changes, for example -- but we haven't done symbol dependencies as 
yet.)

Robert