[Nouveau] [PATCH 1/2] nvfx: restore BEGIN_RING usage

[Michel Hermier]

After cleaning my tree to match this change, I noticed a small
potential issue which is not very likely to happens but still migth
exist. The MARK_RING required to check OUT_RELOC calls are not
updated. The issue is small since whe most probably will runout off
pushbuffer space before runing out of relocs and the relocs is well
protected introducing only graphical issues.
Since you known how to use coccocinelle could you check that the
BEGIN_RING followed by OUT_RELOC are guarded with a MARK_RING?


2010/12/25 Xavier Chantry <chantry.xavier at gmail.com>:
> Michel Hermier reported libdrm segfault (and kernel crash) on nv40 using
> gallium :
> http://www.mail-archive.com/nouveau@lists.freedesktop.org/msg06563.html
>
> It turns out these were caused by some missing WAIT_RING (or wrong
> computation of the WAIT_RING sizes). Unlike all other libdrm_nouveau users,
> nvfx gallium tried to use a mininum calls of WAIT_RING, one WAIT_RING could
> apply to many methods for different code paths and spread across several
> functions. This made it too tricky to find out what the missing or wrong
> WAIT_RING was.
>
> By restoring BEGIN_RING, we force one WAIT_RING per method, and it's much
> easier to check if the free size required in the pushbuffer is correct.  As
> curro said, "let's keep it simple for the maintainers until the big
> bottlenecks are gone"
>
> Benchmarked on nv35 with openarena, nexuiz and ut2004 and no performance
> regression.
>
> The core of this patch was made with Coccinelle, with minor manual fixes
> made on top.