[Intel-gfx] [PATCH 2/2] drm/i915: Flush request queue when waiting for ring space

[Ben Widawsky]

On Mon, May 05, 2014 at 09:07:33AM +0100, Chris Wilson wrote:
> During the review of
> 
> commit 1f70999f9052f5a1b0ce1a55aff3808f2ec9fe42
> Author: Chris Wilson <chris at chris-wilson.co.uk>
> Date:   Mon Jan 27 22:43:07 2014 +0000
> 
>     drm/i915: Prevent recursion by retiring requests when the ring is full
> 
> Ville raised the point that our interaction with request->tail was
> likely to foul up other uses elsewhere (such as hang check comparing
> ACTHD against requests).
> 
> However, we also need to restore the implicit retire requests that certain
> test cases depend upon (e.g. igt/gem_exec_lut_handle), this raises the
> spectre that the ppgtt will randomly call i915_gpu_idle() and recurse
> back into intel_ring_begin().

Forgive my ignorance. Why is i915_gpu_idle() randomly being called for
PPGTT? I don't see anything PPGTT specific here.

[snip]

-- 
Ben Widawsky, Intel Open Source Technology Center