[Intel-gfx] [PATCH v3] drm/i915: Add fault injection support

[Imre Deak]

On Wed, 2016-03-16 at 09:24 +0000, Chris Wilson wrote:
> On Wed, Mar 16, 2016 at 11:18:04AM +0200, Joonas Lahtinen wrote:
> > On ti, 2016-03-15 at 14:14 +0000, Chris Wilson wrote:
> > > On Tue, Mar 15, 2016 at 04:01:14PM +0200, Imre Deak wrote:
> > > > 
> > > > I'm not sure if you want to check all failure paths, I think
> > > > for that
> > > > the existing failslab etc. mechanisms are better suited. This
> > > > new
> > > > option would be used at relatively few well defined places. The
> > > > option
> > > > is a mask since Chris wanted the possibility to mix failures
> > > > (which
> > > > makes sense when injecting a non-fatal failure somewhere). If
> > > > he
> > > > doesn't insist on that possibility I can convert the mask
> > > > option to a
> > > > counter based one identifying a single failure spot instead as
> > > > you
> > > > suggest. Chris?
> > > We can extend the counter mechanism by having multiple counters
> > > behind
> > > i915.inject_load_failure (i.e. =gem:4,driver:10,modeset:1)
> > 
> > Now that there's a series to split down the init functions nicely,
> > one
> > could use the function names directly. By stripping parts of it if
> > needed to shorten them.
> 
> That's nice. Advantage for using counters is that we can write a test
> to
> iterate over the first thousand and have it run against future
> faultpointers. Advantage for using names is that it is readable and
> easily extensible.
> 
> What we could do for testing is record the available fault injection
> points for debugfs and so have the tests automatically adjust (given
> a
> working start point). Overkill?

I'd prefer if we could fine grain things once we have more failure
points. Atm the ones we defined cause driver init to fail, so separate 
counters wouldn't bring us much. I suggest that we keep the module
option as a simple integer for now and extend it later to support the
above tagged counter mechanism and debugfs interface. Here is what I
planned to submit to the list:

https://github.com/ideak/linux/commits/driver_init_refactor

Comments?

--Imre