On Wed, 5 Jun 2019 at 13:08, Daniel Vetter <daniel.vetter@xxxxxxxx> wrote: > > This completes Emil's series of removing DRM_UNLOCKED from modern > drivers. It's entirely cargo-culted since we ignore it on > non-DRIVER_LEGACY drivers since: > > commit ea487835e8876abf7ad909636e308c801a2bcda6 > Author: Daniel Vetter <daniel.vetter@xxxxxxxx> > Date: Mon Sep 28 21:42:40 2015 +0200 > > drm: Enforce unlocked ioctl operation for kms driver ioctls > > Now justifying why we can do this for legacy drives too (and hence > close the source of all the bogus copypasting) is a bit more involved. > DRM_UNLOCKED was introduced in: > > commit ed8b67040965e4fe695db333d5914e18ea5f146f > Author: Arnd Bergmann <arnd@xxxxxxxx> > Date: Wed Dec 16 22:17:09 2009 +0000 > > drm: convert drm_ioctl to unlocked_ioctl > > As a immediate hack to keep i810 happy, which would have deadlocked > without this trickery. The old BKL is automatically dropped in > schedule(), and hence the i810 vs. mmap_sem deadlock didn't actually > cause a real deadlock. But with a mutex it would. The solution was to > annotate these as DRM_UNLOCKED and mark i810 unsafe on SMP machines. > > This conversion caused a regression, because unlike the BKL a mutex > isn't dropped over schedule (that thing again), which caused a vblank > wait in one thread to block the entire desktop and all its apps. Back > then we did vblank scheduling by blocking in the client, awesome isn't > it. This was fixed quickly in (ok not so quickly, took 2 years): > > commit 8f4ff2b06afcd6f151868474a432c603057eaf56 > Author: Ilija Hadzic <ihadzic@xxxxxxxxxxxxxxxxxxxxxx> > Date: Mon Oct 31 17:46:18 2011 -0400 > > drm: do not sleep on vblank while holding a mutex > > All the other DRM_UNLOCKED annotations for all the core ioctls was > work to reach finer-grained locking for modern drivers. This took > years, and culminated in: > > commit fdd5b877e9ebc2029e1373b4a3cd057329a9ab7a > Author: Daniel Vetter <daniel.vetter@xxxxxxxx> > Date: Sat Dec 10 22:52:54 2016 +0100 > > drm: Enforce BKL-less ioctls for modern drivers > > DRM_UNLOCKED was never required by any legacy drivers, except for the > vblank_wait IOCTL. Therefore we will not regress these old drivers by > going back to where we've been in 2011. For all modern drivers nothing > will change. > > To make this perfectly clear, also add a comment to DRM_UNLOCKED. > > v2: Don't forget about drm_ioc32.c (Michel). Not a source of copypasta > mistakes when creating driver ioctl tables, but better to be > consistent. > Personally I would omit the "Not a source of copupasta..." note. > Cc: Michel Dänzer <michel@xxxxxxxxxxx> > Cc: Emil Velikov <emil.l.velikov@xxxxxxxxx> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> Double-checked that only the VBLACK ioctl retained its annotation and all other core ioctls are DRM_UNLOCKED free. Technically with this change UMS drivers will start using a lock on the listed ioctls. I do not expect this to be a problem and admittedly I did not audit existing userspace. That said, the patch looks reasonable: Acked-by: Emil Velikov <emil.velikov@xxxxxxxxxxxxx> Daniel, can you apply any outstanding DRM_UNLOCKED patches from my series? Thanks Emil _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
