Re: [Intel-gfx] [PATCH 1/2] drm/i915/guc: Improve clean up of busyness stats worker

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On 1/24/2023 16:55, Ceraolo Spurio, Daniele wrote:
On 1/11/2023 5:54 PM, John.C.Harrison@xxxxxxxxx wrote:
From: John Harrison <John.C.Harrison@xxxxxxxxx>

The stats worker thread management was mis-matched between
enable/disable call sites. Fix those up. Also, abstract the cancel
code into a helper function rather than replicating in multiple places.

Signed-off-by: John Harrison <John.C.Harrison@xxxxxxxxx>
---
  .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 22 ++++++++++++-------
  1 file changed, 14 insertions(+), 8 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 b436dd7f12e42..982364777d0c6 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -1435,19 +1435,25 @@ static void guc_init_engine_stats(struct intel_guc *guc)
  {
      struct intel_gt *gt = guc_to_gt(guc);
      intel_wakeref_t wakeref;
+    int ret;
        mod_delayed_work(system_highpri_wq, &guc->timestamp.work,
               guc->timestamp.ping_delay);
  -    with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref) {
-        int ret = guc_action_enable_usage_stats(guc);
+    with_intel_runtime_pm(&gt->i915->runtime_pm, wakeref)
+        ret = guc_action_enable_usage_stats(guc);
  -        if (ret)
-            drm_err(&gt->i915->drm,
-                "Failed to enable usage stats: %d!\n", ret);
+    if (ret) {
+        cancel_delayed_work_sync(&guc->timestamp.work);

Wouldn't it be easier to just call mod_delayed_work after the H2G if ret==0, instead of having it before and cancelling if we get a failure?

+        drm_err(&gt->i915->drm, "Failed to enable usage stats: %d!\n", ret);
      }
  }
  +static void guc_park_engine_stats(struct intel_guc *guc)
+{
+    cancel_delayed_work_sync(&guc->timestamp.work);
+}
+

Now you're asymmetric with the park/unpark, because on the park side you have this wrapper, while on the unpark side you directly call mod_delayed_work.
The point is that submission disable needs to also cancel the worker. But calling the actual busyness park function seems excessive - no need to do all the updating if we are about to reset the GuC or unload the driver.

Thinking about it more, calling this park_engine_stats is actually wrong given that engine stats and busyness are the same thing, so basically we would have two functions with the same name where one is a subset of the other. Is it simpler (and safe?) to just call the full busyness unpark from submission_disable? Or is it better to have a cancel/enable_busyness_worker() pair for all instances of turning the worker on or off?

John.



Daniele

  void intel_guc_busyness_park(struct intel_gt *gt)
  {
      struct intel_guc *guc = &gt->uc.guc;
@@ -1460,7 +1466,7 @@ void intel_guc_busyness_park(struct intel_gt *gt)
       * and causes an unclaimed register access warning. Cancel the worker
       * synchronously here.
       */
-    cancel_delayed_work_sync(&guc->timestamp.work);
+    guc_park_engine_stats(guc);
        /*
       * Before parking, we should sample engine busyness stats if we need to. @@ -4409,11 +4415,11 @@ void intel_guc_submission_enable(struct intel_guc *guc)
      guc_init_global_schedule_policy(guc);
  }
  +/* Note: By the time we're here, GuC may have already been reset */
  void intel_guc_submission_disable(struct intel_guc *guc)
  {
      struct intel_gt *gt = guc_to_gt(guc);
-
-    /* Note: By the time we're here, GuC may have already been reset */
+    guc_park_engine_stats(guc);
        /* Disable and route to host */
      if (GRAPHICS_VER(gt->i915) >= 12)





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