Re: [PATCH 2/2] drm/ttm: use RCU to pipeline evictions

On Tue, Jul 5, 2016 at 8:30 AM, Christian König deathsimple@vodafone.de wrote:

From: Christian König christian.koenig@amd.com

Could be faster on the read path.

Signed-off-by: Christian König christian.koenig@amd.com

Just one style nit pick below. Beyond that, the series is: Reviewed-by: Alex Deucher alexander.deucher@amd.com

---

drivers/gpu/drm/ttm/ttm_bo.c | 16 ++++++++++------ drivers/gpu/drm/ttm/ttm_bo_util.c | 8 +++++--- 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 66c50ad..7e30f3b 100644 --- a/drivers/gpu/drm/ttm/ttm_bo.c +++ b/drivers/gpu/drm/ttm/ttm_bo.c @@ -797,9 +797,11 @@ static int ttm_bo_add_move_fence(struct ttm_buffer_object *bo, struct fence *fence; int ret;

•   spin_lock(&man->move_lock);
  

•   fence = fence_get(man->move);
  

•   spin_unlock(&man->move_lock);
  

•   rcu_read_lock();
  

•   do
  

•           fence = rcu_dereference(man->move);
  

•   while (unlikely(fence && !fence_get_rcu(fence)));
  

I generally like to see parens with do/while loops.

•   rcu_read_unlock();
  
    if (fence) {
            reservation_object_add_shared_fence(bo->resv, fence);
  

@@ -1304,9 +1306,11 @@ static int ttm_bo_force_list_clean(struct ttm_bo_device *bdev, } spin_unlock(&glob->lru_lock);

•   spin_lock(&man->move_lock);
  

•   fence = fence_get(man->move);
  

•   spin_unlock(&man->move_lock);
  

•   rcu_read_lock();
  

•   do
  

•           fence = rcu_dereference(man->move);
  

•   while (unlikely(fence && !fence_get_rcu(fence)));
  

Same here.

•   rcu_read_unlock();
  
    if (fence) {
            ret = fence_wait(fence, false);
  

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c index 4da0e78..fcd2431 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_util.c +++ b/drivers/gpu/drm/ttm/ttm_bo_util.c @@ -746,6 +746,7 @@ int ttm_bo_pipeline_move(struct ttm_buffer_object *bo, ttm_bo_unref(&ghost_obj);

    } else if (from->flags & TTM_MEMTYPE_FLAG_FIXED) {

•           struct fence *old;
  
            /**
             * BO doesn't have a TTM we need to bind/unbind. Just remember
  

@@ -753,9 +754,10 @@ int ttm_bo_pipeline_move(struct ttm_buffer_object *bo, */

            spin_lock(&from->move_lock);

•           if (!from->move || fence_is_later(fence, from->move)) {
  

•                   fence_put(from->move);
  

•                   from->move = fence_get(fence);
  

•           old = rcu_dereference_protected(from->move, 1);
  

•           if (!old || fence_is_later(fence, old)) {
  

•                   rcu_assign_pointer(from->move, fence_get(fence));
  

•                   fence_put(old);
            }
            spin_unlock(&from->move_lock);
  
  

-- 2.5.0

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