On Tue, Nov 08, 2016 at 10:35:08AM +0000, Chris Wilson wrote: > On Tue, Nov 08, 2016 at 03:54:47PM +0900, Gustavo Padovan wrote: > > From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx> > > > > Hi, > > > > This is yet another version of the DRM fences patches. Please refer > > to the cover letter[1] in a previous version to check for more details. > > Explicit fencing is not a superset of the implicit fences. The driver > may be using implicit fences (on a reservation object) to serialise > asynchronous operations wrt to each other (such as dispatching threads > to flush cpu caches to memory, manipulating page tables and the like > before the flip). Since the user doesn't know about these operations, > they are not included in the explicit fence they provide, at which point > we can't trust their fence to the exclusion of the implicit fences... My thoughts are that in atomic_check drivers just fill in the fence from the reservation_object (i.e. the uapi implicit fencing part). If there's any additional work that's queued up in ->prepare_fb then I guess the driver needs to track that internally, but _only_ for kernel-internally queued work. The reason for that is that with explicit fencing we want to allow userspace to overwrite any existing implicit fences that might hang around. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
