Am 22.09.21 um 14:20 schrieb Tvrtko Ursulin:
On 22/09/2021 13:15, Christian König wrote:
Am 22.09.21 um 13:46 schrieb Tvrtko Ursulin:
On 22/09/2021 11:21, Tvrtko Ursulin wrote:
On 22/09/2021 10:10, 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>
---
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..313afb4a11c7 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 = false;
You can drop this line, especially since it is not a boolean. With
that:
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Having said this, one thing to add in the commit message is some
commentary that although simpler in code, the new implementation has
a lot more atomic instructions due all the extra fence get/put.
Saying this because I remembered busy ioctl is quite an over-popular
one. Thinking about traces from some real userspaces I looked at in
the past.
So I think ack from maintainers will be required here. Because I
just don't know if any performance impact will be visible or not. So
view my r-b as "code looks fine" but I am on the fence if it should
actually be merged. Probably leaning towards no actually - given how
the code is localised here and I dislike burdening old platforms
with more CPU time it could be cheaply left as is.
Well previously we would have allocated memory, which as far as I
know has more overhead than a few extra atomic operations.
It doesn't, it only uses dma_resv_excl_fence and dma_resv_shared_list.
Yeah, ok then that's not really an option any more.
I think Daniel and I are totally on the same page that we won't allow
this RCU dance in the drivers any more.
Regards,
Christian.
Regards,
Tvrtko
On the other hand I could as well stick with dma_resv_get_fences() here.
Regards,
Christian.
Regards,
Tvrtko
Regards,
Tvrtko
+ 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:
