Determining patch impact on a specific config

[Nicholas Mc Guire]

On Wed, Aug 17, 2016 at 03:52:16PM +0200, Greg KH wrote:
> On Wed, Aug 17, 2016 at 03:25:44PM +0200, Greg KH wrote:
> > On Wed, Aug 17, 2016 at 12:39:39PM +0000, Nicholas Mc Guire wrote:
> > > 
> > > Hi !
> > > 
> > >  For a given patch I would like to find out if it impacts a
> > >  given configuration or not. Now of course one could compile the
> > >  kernel for the configuration prior to the patch, then apply the
> > >  patch and recompile to find out if there is an impact but I would
> > >  be looking for some smarter solution. Checking files only 
> > >  unfortunately will not do it, due to ifdefs and friends so make
> > >  would detect a change and recompile even if the affeted code 
> > >  area is actualy dropped by the preprocessor.
> > > 
> > >  What Im trying to do is find out is, how many of the e.g. stable
> > >  fixes of 4.4-4.4.14 would have impacted a given configuration - the
> > >  whole exercise is intended for some statistical analysis of bugs
> > >  in linux-stable.
> 
> Also, are you going to be analyizing the bugs in the stable trees, or
> the ones we just happen to fix?
> 
> Note, that's not always the same thing :)
>
what we have been looking at first is the stable fixes
for which the bug-commit is known via Fixes: patch. That only
a first approximation but correlates very good with the
overall stable fix rates. And from the regression analysis
of the stable fix rates over versions one then can exstimate the
residual bugs if one knows the distribution of the bug 
survival times - which one again can estimate based on the
bug-fixes that have Fixes: tags. 

I dont know yet how robust these models will be at the end
but from what we have until now I do think we can come up
with quite sound predictions for the residual faults in the
kernel.

Some early results where presented at ALS in Japan on July 14th
but this still needs quite a bit of work.

thx!
hofrat