drm/i915: Add smp_rmb() to busy ioctl's RCU dance
authorChris Wilson <chris@chris-wilson.co.uk>
Tue, 9 Aug 2016 08:23:33 +0000 (09:23 +0100)
committerChris Wilson <chris@chris-wilson.co.uk>
Tue, 9 Aug 2016 09:17:26 +0000 (10:17 +0100)
commitedf6b76f64a2f62b81ed796fe2ce6dd664351d64
treefe8f513eb432134916eb2be6df52fd5dc077fdb5
parent87b723a16de9ff95e2b7d61dbd86bddd3c1716d9
drm/i915: Add smp_rmb() to busy ioctl's RCU dance

In the debate as to whether the second read of active->request is
ordered after the dependent reads of the first read of active->request,
just give in and throw a smp_rmb() in there so that ordering of loads is
assured.

v2: Explain the manual smp_rmb()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1470731014-6894-1-git-send-email-chris@chris-wilson.co.uk
drivers/gpu/drm/i915/i915_gem.c
drivers/gpu/drm/i915/i915_gem_request.h