On Mon, Sep 11, 2023 at 08:44:39AM -0700, Daniele Ceraolo Spurio wrote:
On 9/8/2023 10:16 PM, Umesh Nerlige Ramappa wrote:
The worker is canceled in the __gt_park path, but we still see it
running sometimes during suspend. This is likely because some code is
getting a gt wakeref in the __gt_park path.
This possible root-cause doesn't seem plausible to me, because a gt
wakeref would cause an unpark, so taking it within the park would probably
cause a deadlock. Is it not more likely that the worker re-queued itself?
Will drop the likely part. The worker running during suspend is the
issue, so keeping that part.
Only update stats if gt is awake. If not, intel_guc_busyness_park would
have already updated the stats. Note that we do not requeue the worker
if gt is not awake since intel_guc_busyness_unpark would do that at some
point.
If the gt was parked longer than time taken for GT timestamp to roll
over, we ignore those rollovers since we don't care about tracking the
exact GT time. We only care about roll overs when the gt is active and
running workloads.
Closes: [1]https://gitlab.freedesktop.org/drm/intel/-/issues/7077
This needs a fixes tag. Also, I'm not 100% sure but I believe we prefer
"Link" to "Closes".
I thought Link was mostly for the patchworks link. I can change this to
Link.
Any idea if there is a document/link that explains which tag to use for
what? I have been confused by this before.
Signed-off-by: Umesh Nerlige Ramappa [2]<umesh.nerlige.ramappa@xxxxxxxxx>
---
.../gpu/drm/i915/gt/uc/intel_guc_submission.c | 27 ++++++++++++++++---
1 file changed, 23 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
index e250bedf90fb..df31d6047ce9 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -1457,10 +1457,27 @@ static void guc_timestamp_ping(struct work_struct *wrk)
struct intel_uc *uc = container_of(guc, typeof(*uc), guc);
struct intel_gt *gt = guc_to_gt(guc);
struct intel_context *ce;
- intel_wakeref_t wakeref;
unsigned long index;
int srcu, ret;
+ /*
+ * The worker is canceled in the __gt_park path, but we still see it
+ * running sometimes during suspend. This is likely because some code
+ * is getting a gt wakeref in the __gt_park path.
Same comment from before about this explanation. I would just remove this
part from the comment.
+ *
+ * Only update stats if gt is awake. If not, intel_guc_busyness_park
+ * would have already updated the stats. Note that we do not requeue the
+ * worker in this case since intel_guc_busyness_unpark would do that at
+ * some point.
+ *
+ * If the gt was parked longer than time taken for GT timestamp to roll
+ * over, we ignore those rollovers since we don't care about tracking
+ * the exact GT time. We only care about roll overs when the gt is
+ * active and running workloads.
+ */
+ if (!intel_gt_pm_get_if_awake(gt))
+ return;
+
Do we need to drop the _sync from the busyness stats worker parking if we
take the gt_pm wakeref in here, instead of an rpm one? because if the
gt_pm_put below causes a park and the park waits on this worker to
complete then we'll deadlock.
Hmm, My bad, That's not what I intended. It should be
intel_runtime_pm_get_if_active(). I will change that
/*
* Synchronize with gt reset to make sure the worker does not
* corrupt the engine/guc stats. NB: can't actually block waiting
@@ -1468,17 +1485,19 @@ static void guc_timestamp_ping(struct work_struct *wrk)
* this worker thread if started. So waiting would deadlock.
*/
ret = intel_gt_reset_trylock(gt, &srcu);
- if (ret)
+ if (ret) {
+ intel_gt_pm_put(gt);
return;
+ }
- with_intel_runtime_pm(>->i915->runtime_pm, wakeref)
- __update_guc_busyness_stats(guc);
+ __update_guc_busyness_stats(guc);
/* adjust context stats for overflow */
xa_for_each(&guc->context_lookup, index, ce)
guc_context_update_stats(ce);
intel_gt_reset_unlock(gt, srcu);
+ intel_gt_pm_put(gt);
I think this needs to go after the queuing, because it could cause a park
and if it does we don't want to re-queue the worker immediately after,
while if we queue it before then the park will cancel it.
Non-blocking style comment: with gt_pm_put the last thing in function, you
can also transform that early return in a "goto put;" and have a single
place for the gt_put.
Will change, although I am not sure if the runtime pm put may also cause
a gt park. Assuming it can, I will make these changes.
Thanks
Umesh
Daniele
guc_enable_busyness_worker(guc);
}
References
Visible links
1. https://gitlab.freedesktop.org/drm/intel/-/issues/7077
2. mailto:umesh.nerlige.ramappa@xxxxxxxxx
