CHROMIUM: drm/udl: serialize all URB access

The URB access in udl_modeset.c needs to be serialized with those
in udl_handle_damage().

BUG=chromium:581838,chromium:1091891,b:156523992
TEST=verify no crash when closing lid with 2 UDL devices attached

(cherry picked from commit 9db56bc46ca4eefb3f12ba740a78537720df2cac)
Reviewed-on: https://chromium-review.googlesource.com/377085

Change-Id: I6b07e2e544eada5c7f50287f55d46807b6b067fd
Signed-off-by: Joe Tessler <jrt@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2233540
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Commit-Queue: Ilja H. Friedel <ihf@chromium.org>
(cherry picked from commit 60e406876eb50cb29376e89f65535c431975bd0f)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2278426
1 file changed