[Intel-gfx] PROBLEM: i915 causes complete desktop freezes in 4.15-rc5

[Chris Wilson]

Quoting Alexandru Chirvasitu (2018-01-05 19:37:24)
> I'll try. I need a bit of clarification:
> 
> On Fri, Jan 05, 2018 at 05:52:25PM +0000, Chris Wilson wrote:
> > Quoting Alexandru Chirvasitu (2018-01-03 21:53:15)
> > > All right, here's the dmesg from the kernel compiled from drm-tip (in
> > > sync with upstream at the time of the compilation earlier today), with
> > > 
> > > CONFIG_DRM_I915_DEBUG_GEM=y
> > > 
> > > I crashed it by opening 20+ xterm windows. Doesn't always do it though
> > > (tried this before).
> > 
> > Sorry, still stumped. It's still the same use-after-free and no asserts
> > hit. Can you keep KASAN enabled but disable slab/page poisoning? Hmm, I
> > think it has to be page poisoning doing the 0x6b as SLAB_POISON is
> > disabled by default.
> 
> Would this have to be through a new compilation, or would it do to
> just remove the poisoning kernel parameter on boot? 

CONFIG_PAGE_POISONING

> 
> > (You could check by enabling slabstats can looking in sysfs.)
> 
> Sorry, I was having some trouble parsing this; what do I check again
> and how?
> 
> Does 'slabstats' refer to another kernel config option or something
> else?

It would be CONFIG_SLUB_STATS and then you would a
/sys/kernel/slab/i915_dependency/ directory with all the details of the
slab, and in particular a poison file showing the status (and allowing
it to modified) of slab poisoning

Ok, it looks like poisoning is only available if CONFIG_SLUB_DEBUG is
set. Since it is not set, don't worry about it ;)
-Chris