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authorDaniel Vetter <daniel.vetter@ffwll.ch>2019-06-05 14:08:35 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2019-06-21 19:13:10 +0200
commit75426367cd377120a256cad0b35b02eec4b83591 (patch)
tree3a0b8df22c8cb89487ec75a69eba57fb7f55e9d1 /include/drm/drm_ioctl.h
parente4fa8457b2197118538a1400b75c898f9faaf164 (diff)
downloadlinux-75426367cd377120a256cad0b35b02eec4b83591.tar.bz2
drm/ioctl: Ditch DRM_UNLOCKED except for the legacy vblank ioctl
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@ffwll.ch> 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@arndb.de> 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@research.bell-labs.com> 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@ffwll.ch> 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). Cc: Michel Dänzer <michel@daenzer.net> Cc: Emil Velikov <emil.l.velikov@gmail.com> Acked-by: Emil Velikov <emil.velikov@collabora.com> Acked-by: Michel Dänzer <michel@daenzer.net> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190605120835.2798-1-daniel.vetter@ffwll.ch
Diffstat (limited to 'include/drm/drm_ioctl.h')
-rw-r--r--include/drm/drm_ioctl.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/drm/drm_ioctl.h b/include/drm/drm_ioctl.h
index fafb6f592c4b..10100a4bbe2a 100644
--- a/include/drm/drm_ioctl.h
+++ b/include/drm/drm_ioctl.h
@@ -114,6 +114,9 @@ enum drm_ioctl_flags {
* Whether &drm_ioctl_desc.func should be called with the DRM BKL held
* or not. Enforced as the default for all modern drivers, hence there
* should never be a need to set this flag.
+ *
+ * Do not use anywhere else than for the VBLANK_WAIT IOCTL, which is the
+ * only legacy IOCTL which needs this.
*/
DRM_UNLOCKED = BIT(4),
/**