On Fri, Mar 10, 2017 at 11:01:54AM -0500, Sean Paul wrote: > On Fri, Mar 10, 2017 at 02:12:14PM +1000, Dave Airlie wrote: > > Talk to Jonas (jadahl) on irc, he had 3 mutters running and on hotplug > > all 3 of them were diving into the connector getting code. Now I think > > we can avoid this in userspace by not probing when not owning the VT, > > but it's still messy behaviour. > > > > It looks like one thread does a getconnector, this fills out the EDID > > blob with a specific blob id, > > then second thread does getconnector, which replaces the EDID blob > > with another one > > the first thread calls get property blob, but the blob id it is > > looking for is destroyed. > > > > Ideas? > > I think you could probably fix this by introducing a new > drm_property_overwrite_global_blob() function. If the size of the current blob is > the same as the new blob, you could just overwrite the data and preserve the id > and references. You could then replace the drm_property_replace_global_blob() call in > drm_mode_connector_update_edid_property() to call the new function. Of course, > you would need to fall back on *replace_global_blob() if size differed, but it > would probably solve the issue above. blobs are imutable (not that userspace can use that much since we can reuse ids), I think if we do this we should compare the contents of the blob. > That said, I'm not convinced it should be kernel's responsibility to really > solve this problem. How much effort should we put into mitigating the effects of > a racey and wasteful userspace? It's a tradeoff between "why should the kernel care" and "every compositor will get this wrong". Maybe something like libweston will fix this eventually .... -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
