linux-kernel - Re: PROBLEM: i915 causes complete desktop freezes in 4.15-rc5

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Date:   Fri, 5 Jan 2018 14:37:24 -0500
From:   Alexandru Chirvasitu <achirvasub@...il.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        intel-gfx@...ts.freedesktop.org,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: PROBLEM: i915 causes complete desktop freezes in 4.15-rc5

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? 

> (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?

I apologize, most of these options I'm fiddling with are not familiar
to me..

> My goal is to get that kasan trace telling me who about the
> freed object.
> -Chris