[Intel-gfx] [RFC PATCH 2/2] Fix per client busyness locking

[Ashutosh Dixit]

1. Do all ce->stats updates and reads under guc->timestamp.lock
2. Pin context image before reading
3. Merge __guc_context_update_clks and guc_context_update_stats into a
   single function
4. Call lrc_update_runtime() unconditionally in guc_context_update_stats
5. Seems no need to update ce->stats.active with this approach

Some of the above steps may not be correct or complete but the idea is to
discuss/improve the original patch.

Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
---
 drivers/gpu/drm/i915/gt/intel_context.c       |  2 +-
 drivers/gpu/drm/i915/gt/intel_context_types.h |  2 +-
 .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 41 ++++++++++---------
 3 files changed, 24 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index e2d70a9fdac0..c004f676de27 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -581,7 +581,7 @@ u64 intel_context_get_total_runtime_ns(struct intel_context *ce)
 	u64 total, active;
 
 	if (ce->ops->update_stats)
-		ce->ops->update_stats(ce);
+		return ce->ops->update_stats(ce);
 
 	total = ce->stats.runtime.total;
 	if (ce->ops->flags & COPS_RUNTIME_CYCLES)
diff --git a/drivers/gpu/drm/i915/gt/intel_context_types.h b/drivers/gpu/drm/i915/gt/intel_context_types.h
index f7ff4c7d81c7..699435bfff99 100644
--- a/drivers/gpu/drm/i915/gt/intel_context_types.h
+++ b/drivers/gpu/drm/i915/gt/intel_context_types.h
@@ -59,7 +59,7 @@ struct intel_context_ops {
 
 	void (*sched_disable)(struct intel_context *ce);
 
-	void (*update_stats)(struct intel_context *ce);
+	u64 (*update_stats)(struct intel_context *ce);
 
 	void (*reset)(struct intel_context *ce);
 	void (*destroy)(struct kref *kref);
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 bee8cf10f749..40d0edaf2e0a 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -1376,7 +1376,6 @@ static void __update_guc_busyness_stats(struct intel_guc *guc)
 	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
 }
 
-static void __guc_context_update_clks(struct intel_context *ce);
 static void guc_timestamp_ping(struct work_struct *wrk)
 {
 	struct intel_guc *guc = container_of(wrk, typeof(*guc),
@@ -1401,7 +1400,8 @@ static void guc_timestamp_ping(struct work_struct *wrk)
 
 	/* adjust context stats for overflow */
 	xa_for_each(&guc->context_lookup, index, ce)
-		__guc_context_update_clks(ce);
+		if (ce->ops->update_stats)
+			ce->ops->update_stats(ce);
 
 	intel_gt_reset_unlock(gt, srcu);
 
@@ -1476,17 +1476,21 @@ void intel_guc_busyness_unpark(struct intel_gt *gt)
 			 guc->timestamp.ping_delay);
 }
 
-static void __guc_context_update_clks(struct intel_context *ce)
+static u64 guc_context_update_stats(struct intel_context *ce)
 {
 	struct intel_guc *guc = ce_to_guc(ce);
 	struct intel_gt *gt = ce->engine->gt;
 	u32 *pphwsp, last_switch, engine_id;
-	u64 start_gt_clk, active;
 	unsigned long flags;
+	u64 total, active = 0;
 	ktime_t unused;
 
+	intel_context_pin(ce);
 	spin_lock_irqsave(&guc->timestamp.lock, flags);
 
+	lrc_update_runtime(ce);
+	total = ce->stats.runtime.total;
+
 	/*
 	 * GPU updates ce->lrc_reg_state[CTX_TIMESTAMP] when context is switched
 	 * out, however GuC updates PPHWSP offsets below. Hence KMD (CPU)
@@ -1502,27 +1506,26 @@ static void __guc_context_update_clks(struct intel_context *ce)
 	guc_update_pm_timestamp(guc, &unused);
 
 	if (engine_id != 0xffffffff && last_switch) {
-		start_gt_clk = READ_ONCE(ce->stats.runtime.start_gt_clk);
-		__extend_last_switch(guc, &start_gt_clk, last_switch);
-		active = intel_gt_clock_interval_to_ns(gt, guc->timestamp.gt_stamp - start_gt_clk);
-		WRITE_ONCE(ce->stats.runtime.start_gt_clk, start_gt_clk);
-		WRITE_ONCE(ce->stats.active, active);
-	} else {
-		lrc_update_runtime(ce);
+		__extend_last_switch(guc, &ce->stats.runtime.start_gt_clk, last_switch);
+		active = intel_gt_clock_interval_to_ns(gt,
+			      guc->timestamp.gt_stamp - ce->stats.runtime.start_gt_clk);
 	}
 
 	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
+	intel_context_unpin(ce);
+
+	return total + active;
 }
 
-static void guc_context_update_stats(struct intel_context *ce)
+void lrc_update_runtime_locked(struct intel_context *ce)
 {
-	if (!intel_context_pin_if_active(ce)) {
-		WRITE_ONCE(ce->stats.runtime.start_gt_clk, 0);
-		WRITE_ONCE(ce->stats.active, 0);
-		return;
-	}
+	struct intel_guc *guc = ce_to_guc(ce);
+	unsigned long flags;
 
-	__guc_context_update_clks(ce);
+	intel_context_pin(ce);
+	spin_lock_irqsave(&guc->timestamp.lock, flags);
+	lrc_update_runtime(ce);
+	spin_unlock_irqrestore(&guc->timestamp.lock, flags);
 	intel_context_unpin(ce);
 }
 
@@ -2780,7 +2783,7 @@ static void guc_context_unpin(struct intel_context *ce)
 {
 	struct intel_guc *guc = ce_to_guc(ce);
 
-	lrc_update_runtime(ce);
+	lrc_update_runtime_locked(ce);
 	unpin_guc_id(guc, ce);
 	lrc_unpin(ce);
 
-- 
2.34.1