On Thu, Apr 19, 2012 at 05:30:03PM +0100, Dave Airlie wrote: > On Thu, Apr 19, 2012 at 5:22 PM, Andy Whitcroft <apw@xxxxxxxxxxxxx> wrote: > > We have been carrying a (rather poor) patch for an issue we identified in > > the DRM driver. This issue is triggered when a DRM device is initialising > > and userspace attempts to open it, typically in response to the sysfs > > device added event. Basically we allocate the minor numbers making > > the device available, and then call the drm load callback. Until this > > completes the device is really not ready and these early opens typically > > lead to oopses. > > > > We have been using the following patch to avoid this by marking the minors > > as in error until the load method has completed. This avoids the early > > open by simply erroring out the opens with EAGAIN. Obviously we should > > be delaying the open until the load method complete. > > > > I include the existing patch for completness (it is not really ready for > > merging) to illustrate the issue. I think it is logical that the wait > > should simply be delayed until the load has completed. I am proposing > > to include a wait queue associated with the idr cache for the drm minors > > which we can use to allow open callers to wait_event_interruptible() on. > > I'll be putting together a prototype shortly and will follow up with it. > > > > Thoughts? > > Couldn't we just delay registering things until the driver is ready to > accept an open? It's somewhere on my eternal&epic todo list. > Granted the midlayer of drm doesn't make that easy, ... after fixing this one ;-) > thanks for sending this out, it keeps falling off my radar, I don't > think I've ever seen this reported on RHEL/Fedora, which makes me > wonder what we are doing that makes us lucky. I think it's just a matter of races, if you load the drm module early enough (like fedora does already in the initrd) and ensure that nothing pokes drm devices for a few seconds, you'll be fine. Iirc ubuntus powerd stuff is really got at brining everything down. Also, not loading the module with udev, but loading it with X resulted in nice fireworks last time I've tried that (radeon ums was trying to set up the card while the kms code was doing the same, hilarity ensued). -Daniel -- Daniel Vetter Mail: daniel@xxxxxxxx Mobile: +41 (0)79 365 57 48 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
