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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2016-08-09 11:23:33 +0300 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2016-08-09 12:17:26 +0300 |
| commit | edf6b76f64a2f62b81ed796fe2ce6dd664351d64 (patch) | |
| tree | fe8f513eb432134916eb2be6df52fd5dc077fdb5 /drivers/gpu/drm/i915/i915_gem_request.h | |
| parent | 87b723a16de9ff95e2b7d61dbd86bddd3c1716d9 (diff) | |
| download | linux-edf6b76f64a2f62b81ed796fe2ce6dd664351d64.tar.xz | |
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
Diffstat (limited to 'drivers/gpu/drm/i915/i915_gem_request.h')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_gem_request.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_request.h b/drivers/gpu/drm/i915/i915_gem_request.h index f6661f31a348..6dd83b172c7a 100644 --- a/drivers/gpu/drm/i915/i915_gem_request.h +++ b/drivers/gpu/drm/i915/i915_gem_request.h @@ -490,6 +490,9 @@ __i915_gem_active_get_rcu(const struct i915_gem_active *active) * incremented) then the following read for rcu_access_pointer() * must occur after the atomic operation and so confirm * that this request is the one currently being tracked. + * + * The corresponding write barrier is part of + * rcu_assign_pointer(). */ if (!request || request == rcu_access_pointer(active->request)) return rcu_pointer_handoff(request); |