[Intel-gfx] [PATCH 4/9] drm/i915: don't free the CFB while FBC is enabled

[Chris Wilson]

On Fri, Dec 26, 2014 at 11:46:49AM -0200, Paulo Zanoni wrote:
> 2014-12-25 8:20 GMT-02:00 Chris Wilson <chris at chris-wilson.co.uk>:
> > On Tue, Dec 23, 2014 at 10:35:40AM -0200, Paulo Zanoni wrote:
> >> From: Paulo Zanoni <paulo.r.zanoni at intel.com>
> >>
> >> Because that is probably not very a good idea: if we used the stolen
> >> memory for more things, there could be a risk that someone would
> >> "allocate" the memory that the HW is still using as the CFB while FBC
> >> was still enabled.
> >
> > Not in the code as it currently is due to the struct mutex lock. You
> > need to explain how and why you intend to remove that invariant.
> 
> Ok, maybe this point is wrong, but I still wee we freeing and then
> reallocating the CFB while FBC is active, which is still a problem,
> even if we end up just reallocating the same chunk of memory later.

No. If you read the current code it will disable FBC using the old
location before it can be reallocated. That it may continue to use the
old address for a frame after we have marked it free isn't clean, but it
is not the bug you describe.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre