On 11/20/2012 07:19 AM, Dave Airlie wrote:
On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom thellstrom@vmware.com wrote:
The mostly used lookup+get put+potential_destroy path of TTM objects is converted to use RCU locks. This will substantially decrease the amount of locked bus cycles during normal operation. Since we use kfree_rcu to free the objects, no rcu synchronization is needed at module unload time.
As this is the first use of RCU in a drm driver from what I can see, let me remind that the RCU patent agreement AFAIK only covers GPL works.
So non-GPL or other OSes porting this code should take not of this.
Dave.
From VMware's side this won't be a problem, since other VMware kernel modules (VMCI IIRC) use RCU.
In any case I have a new version of the "vmwgfx optimization" patch series that mostly add documentation and annotation (by using a drm_ht_xxx_rcu) interface for hashtab, after an internal review by Dmitry Torkov. I see you've already applied the original patch series. Do you want me to send out the new one or rebase it against current drm-next?
Thanks, Thomas