[Intel-gfx] [PATCH] drm/i915: Update write_domains on active list after flush.

[Eric Anholt]

On Sun,  7 Feb 2010 16:20:18 +0100, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> Before changing the status of a buffer with a pending write we will await
> upon a new flush for that buffer. So we can take advantage of any flushes
> posted whilst the buffer is active and pending processing by the GPU, by
> clearing its write_domain and updating its last_rendering_seqno -- thus
> saving a potential flush in deep queues and improves flushing behaviour
> upon eviction for both GTT space and fences.
> 
> In order to reduce the time spent searching the active list for matching
> write_domains, we move those to a separate list whose elements are
> the buffers belong to the active/flushing list with pending writes.
> 
> Orignal patch by Chris Wilson <chris at chris-wilson.co.uk>, forward-ported
> by me.
> 
> In addition to better performance, this also fixes a real bug. Before
> this changes, i915_gem_evict_everything didn't work as advertised. When
> the gpu was actually busy and processing request, the flush and subsequent
> wait would not move active and dirty buffers to the inactive list, but
> just to the flushing list. Which triggered the BUG_ON at the end of this
> function. With the more tight dirty buffer tracking, all currently busy and
> dirty buffers get moved to the inactive list by one i915_gem_flush operation.
> 
> I've left the BUG_ON I've used to prove this in there.
> 
> References:
>   Bug 25911 - 2.10.0 causes kernel oops and system hangs
>   http://bugs.freedesktop.org/show_bug.cgi?id=25911
> 
>   Bug 26101 - [i915] xf86-video-intel 2.10.0 (and git) triggers kernel oops
>               within seconds after login
>   http://bugs.freedesktop.org/show_bug.cgi?id=26101
> 
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Awesome, thanks!  Applied to for-linus with the bonus s-o-b and tested-by.
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