On Wed, May 23, 2018 at 2:59 PM, Qiang Yu <yuq825@xxxxxxxxx> wrote: > On Wed, May 23, 2018 at 5:04 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: >> On Tue, May 22, 2018 at 09:04:17AM +0800, Qiang Yu wrote: >>> On Tue, May 22, 2018 at 3:37 AM, Eric Anholt <eric@xxxxxxxxxx> wrote: >>> > Qiang Yu <yuq825@xxxxxxxxx> writes: >>> > >>> >> This reverts commit 45c3d213a400c952ab7119f394c5293bb6877e6b. >>> >> >>> >> lima driver need preclose to wait all task in the context >>> >> created within closing file to finish before free all the >>> >> buffer object. Otherwise pending tesk may fail and get >>> >> noisy MMU fault message. >>> >> >>> >> Move this wait to each buffer object free function can >>> >> achieve the same result but some buffer object is shared >>> >> with other file context, but we only want to wait the >>> >> closing file context's tasks. So the implementation is >>> >> not that straight forword compared to the preclose one. >>> > >>> > You should just separate your MMU structures from drm_file, and have >>> > drm_file and the jobs using it keep a reference on them. This is what >>> > I've done in V3D as well. >>> >>> It's not the VM/MMU struct that causes this problem, it's each buffer >>> object that gets freed before task is done (postclose is after buffer free). >>> If you mean I should keep reference of all buffers for tasks, that's not >>> as simple as just waiting task done before free buffers. >> >> Why can't you do that waiting in the postclose hook? If it's the lack of >> reference-counting in your driver for gem bo, then I'd say you need to >> roll out some reference counting. Relying on the implicit reference >> provided by the core is kinda not so great (which was the reason I've >> thrown out the preclose hook). There's also per-bo open/close hooks. > > It's possible to not use preclose, but the implementation is not as simple > and straight forward as the preclose I think. There're two method I can > think of: > 1. do wait when free buffers callback unmap buffer from this process's > lima VM (wait buffer reservation object), this is fine and simple, but > there's case that this buffer is shared between two processes, so the > best way should be only waiting fences from this process, so we'd > better do some record for fences for a "perfect waiting" > 2. keep a reference of involved buffers for a task, unreference it when > task done, also keep a reference of the buffer mapping in this process's > lima VM (this is more complicated to implement) > > But if there's a preclose, just wait all this process's task done, then > unmap/free buffers, it's simple and straight forward. I'd like to hear if > there's other better way for only use postclose. Refcount your buffers. Borrowing references from other places tends to result in a maintenance headache with no end. So solution 2. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
