On 21/09/2021 10:41, Christian König wrote:
Am 20.09.21 um 12:33 schrieb Tvrtko Ursulin:
On 20/09/2021 11:13, Christian König wrote:
Am 20.09.21 um 10:45 schrieb Tvrtko Ursulin:
On 17/09/2021 13:35, 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 | 32
++++++++----------------
1 file changed, 11 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..b1cb7ba688da 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 +109,17 @@ 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;
+ dma_resv_iter_begin(&cursor, obj->base.resv, true);
+ dma_resv_for_each_fence_unlocked(&cursor, fence) {
You did not agree with my suggestion to reset args->busy on restart
and so preserve current behaviour?
No, I want to keep the restart behavior internally to the dma_resv
object and as far as I can see it should not make a difference here.
To be clear, on paper difference between old and new implementation is
if the restart happens while processing the shared fences.
Old implementation unconditionally goes to "args->busy =
>>> busy_check_writer(dma_resv_excl_fence(obj->base.resv));" and so
overwrites the set of flags returned to userspace.
New implementation can merge new read flags to the old set of flags
and so return a composition of past and current fences.
Maybe it does not matter hugely in this case, depends if userspace
typically just restarts until flags are clear. But I am not sure.
On the higher level - what do you mean with wanting to keep the
restart behaviour internal? Not providing iterators users means of
detecting it? I think it has to be provided.
Ok I will adjust that for now to get the patch set upstream. But in
general when somebody outside of the dma_resv code base depends on the
restart behavior then that's a bug inside the design of that code.
Thanks, no change in behaviour makes for an easy r-b. :)
The callers should only care about what unsignaled fences are inside the
dma_resv container and it shouldn't matter if those fences are presented
once or multiple times because of a reset..
When this makes a difference we have a bug in the handling and should
probably consider taking the dma_resv.lock instead.
I agree, which is why I was mentioning earlier how it would be good to
completely sort locked from unlocked iterators and avoid situations
where unlocked one is called from a path where object is locked.
Unfortunately for the display code path I cannot easily help with the
audit of call paths. And I think there are at least two patches in your
series which need KMS expertise.
Regards,
Tvrtko
