On Fri, Jan 15, 2016 at 3:10 PM, Dave Airlie <airl...@gmail.com> wrote: >> >> well, nothing specific, but for example early on we had some confusion >> in drm_gralloc (when adding dmabuf fd support) about who close()d the >> fd's. Resulting in same fd getting closed twice (although some >> completely unrelated file handle might have snuck into that slot >> between the two close()s). >> >> Or you could end up w/ the same sort of thing for gem handles (which >> are unique to the drm device fd, so if you open() the device multiple >> times..). I did initially have some confusion about this, w/ multiple >> fd_bo's (or pipe_resource's) being created for a given gem handle, and >> first one that gets deleted takes away the backing store that both >> userspace references where using. >> >> You might want to look at freedreno_drm_winsys.c and the crazy things >> it does.. I suspect virgl might need similar hacks. That is really >> one part of two, that ensures that we share the same pipe_screen, and >> therefore (from libdrm) fd_device, for a given drm device fd. The >> other part is that fd_device has hashtables to deal w/ double import >> of gem buffers. > > I think Rob Clark might be on the right track here. > > it sounds like the host is sending double deletes for some objects, which > sounds like a possible reference counting bug in the host. > > So possibly something drm_gralloc, but it could be a bug in mesa, though > I haven't triggered anything like this yet.
Some more details. If I comment out the freeing of imported buffers in gralloc_drm_handle_unregister, things work a lot better. I think there is a missing reference taken on an alloc with an existing dmabuf FD. I've been comparing freedreno vs. pipe alloc/free implementations for gralloc. The freedreno alloc function will call drmPrimeFDToHandle and increment the BO ref count (in lookup_bo). The equivalent for virgl is in virgl_drm_winsys_resource_create_handle. It calls drmPrimeFDToHandle, but there is no reference taken. The shared handle case in that function does take a reference with a virgl_drm_resource_reference call. I may be off as my attempted fix doesn't work... Rob _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
