Re: [git pull] drm fixes for 2.6.27-rc1

[Keith P. <ke...@ke...>]

On Thu, 2008-10-23 at 18:10 +0200, Thomas Hellström wrote:

> I haven't looked into the code for a while, but isn't it possible to use 
> a spinlock (_bh) for ring protection?

Because we may have to wait for the hardware to drain the ring, it
wouldn't be a good idea to hold a spinlock. In the worst case, with the
hardware locked up, you will have wedged the entire machine.

> Or perhaps even the hardware ring lock bit? Or are you protecting other 
> things with the ring mutex as well?

It can still take a long time to wait for the hardware, so we want to
allow other tasks to run.

Using the separate high-priority ring will allow us to insert commands
into that ring and have it automatically interrupt the main ring
execution, all without needing to wait for access to the main ring.

-- 
kei...@in...