[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.rama...@intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.di...@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