[Bug 109823] [CI][DRMTIP] igt at gem_ppgtt@blt-vs-render-ctx0 - dmesg-fail - BUG: unable to handle kernel paging request at ffffa08d71663ee0

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=109823

--- Comment #6 from Martin Peres <martin.peres at free.fr> ---
(In reply to Chris Wilson from comment #4)
> If it's stray memcorruption (honestly more likely than a bug in the swap
> code), then 
> 
> commit e781a7a3235e9ff68095d2cd4d9c1e039a0516d7
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Mon Mar 4 11:41:13 2019 +0000
> 
>     drm/i915: Acquire breadcrumb ref before cancelling
>     
>     We may race the interrupt signaling with retirement, in which case the
>     order in which we acquire the reference inside the interrupt is vital to
>     provide the correct barrier against the request being freed in
>     retirement, i.e. we need to acquire our reference before marking the
>     breadcrumb as cancelled (as soon as the breadcrumb is cancelled
>     retirement may drop its reference to the request without serialisation
>     with the interrupt handler).
> 
> is definitely a possible fix. But without definite proof, the only thing we
> can do is read the code while waiting for a pattern.

Seen only once, 22 drmtip runs ago. I guess we'll have to wait quite a long
time before closing this one...

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