Am 05.10.21 um 14:40 schrieb Tvrtko Ursulin:
On 05/10/2021 12:37, Christian König wrote:
This makes the function much simpler since the complex
retry logic is now handled else where.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reminder - r-b was retracted until at least more text is added to
commit message about pros and cons. But really some discussion had
inside the i915 team on the topic.
Sure, going to move those to a different branch.
But I really only see the following options:
1. Grab the lock.
2. Use the _unlocked variant with get/put.
3. Add another _rcu iterator just for this case.
I'm fine with either, but Daniel pretty much already rejected #3 and
#2/#1 has more overhead then the original one.
Regards,
Christian.
Regards,
Tvrtko
---
drivers/gpu/drm/i915/gem/i915_gem_busy.c | 35 ++++++++++--------------
1 file changed, 14 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
index 6234e17259c1..dc72b36dae54 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c
@@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void
*data,
{
struct drm_i915_gem_busy *args = data;
struct drm_i915_gem_object *obj;
- struct dma_resv_list *list;
- unsigned int seq;
+ struct dma_resv_iter cursor;
+ struct dma_fence *fence;
int err;
err = -ENOENT;
@@ -109,27 +109,20 @@ i915_gem_busy_ioctl(struct drm_device *dev,
void *data,
* to report the overall busyness. This is what the wait-ioctl
does.
*
*/
-retry:
- seq = raw_read_seqcount(&obj->base.resv->seq);
-
- /* Translate the exclusive fence to the READ *and* WRITE engine */
- args->busy =
busy_check_writer(dma_resv_excl_fence(obj->base.resv));
-
- /* Translate shared fences to READ set of engines */
- list = dma_resv_shared_list(obj->base.resv);
- if (list) {
- unsigned int shared_count = list->shared_count, i;
-
- for (i = 0; i < shared_count; ++i) {
- struct dma_fence *fence =
- rcu_dereference(list->shared[i]);
-
+ args->busy = 0;
+ dma_resv_iter_begin(&cursor, obj->base.resv, true);
+ dma_resv_for_each_fence_unlocked(&cursor, fence) {
+ if (dma_resv_iter_is_restarted(&cursor))
+ args->busy = 0;
+
+ if (dma_resv_iter_is_exclusive(&cursor))
+ /* Translate the exclusive fence to the READ *and* WRITE
engine */
+ args->busy |= busy_check_writer(fence);
+ else
+ /* Translate shared fences to READ set of engines */
args->busy |= busy_check_reader(fence);
- }
}
-
- if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq))
- goto retry;
+ dma_resv_iter_end(&cursor);
err = 0;
out:
