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

[Chris Wilson]

On Wed, Mar 16, 2016 at 11:43:14AM +0200, Imre Deak wrote:
> 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

Move the inline into __i915_inject_load_failure, and yes I am happy with
the simple first step.  Please use __func__ or __FUNCTION__ though as
that is more descriptive than file, especially when they move.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre