On Fri, Jun 8, 2012 at 3:56 PM, Erik Gilling <konkers at android.com> wrote: >> I guess my other thought is that implicit vs explicit is not >> mutually exclusive, though I'd guess there'd be interesting >> deadlocks to have to debug if both were in use _at the same >> time_. :-) > > I think this is an approach worth investigating. ?I'd like a way to > either opt out of implicit sync or have a way to check if a dma-buf > has an attached fence and detach it. ?Actually, that could work really > well. Consider: > > * Each dma_buf has a single fence "slot" > * on submission > ? * the driver will extract the fence from the dma_buf and queue a wait on it. > ? * the driver will replace that fence with it's own complettion > fence before the job submission ioctl returns. > * dma_buf will have two userspace ioctls: > ? * DETACH: will return the fence as an FD to userspace and clear the > fence slot in the dma_buf > ? * ATTACH: takes a fence FD from userspace and attaches it to the > dma_buf fence slot. ?Returns an error if the fence slot is non-empty. > > In the android case, we can do a detach after every submission and an > attach right before.
btw, I like this idea for implicit and explicit sync to coexist BR, -R
