drm/i915: Refine i915_reset.lock_map

We already use a mutex to serialise i915_reset() and wedging, so all we
need it to link that into i915_request_wait() and we have our lock cycle
detection.

v2.5: Take error mutex for selftests
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190614071023.17929-3-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_reset.c

@@ -978,7 +978,7 @@ void i915_reset(struct drm_i915_private *i915,
 
 	might_sleep();
 	GEM_BUG_ON(!test_bit(I915_RESET_BACKOFF, &error->flags));
-	lock_map_acquire(&i915->gt.reset_lockmap);
+	mutex_lock(&error->wedge_mutex);
 
 	/* Clear any previous failed attempts at recovery. Time to try again. */
 	if (!__i915_gem_unset_wedged(i915))
@@ -1031,7 +1031,7 @@ void i915_reset(struct drm_i915_private *i915,
 finish:
 	reset_finish(i915);
 unlock:
-	lock_map_release(&i915->gt.reset_lockmap);
+	mutex_unlock(&error->wedge_mutex);
 	return;
 
 taint:
@@ -1147,9 +1147,7 @@ static void i915_reset_device(struct drm_i915_private *i915,
 		/* Flush everyone using a resource about to be clobbered */
 		synchronize_srcu_expedited(&error->reset_backoff_srcu);
 
-		mutex_lock(&error->wedge_mutex);
 		i915_reset(i915, engine_mask, reason);
-		mutex_unlock(&error->wedge_mutex);
 
 		intel_finish_reset(i915);
 	}

drivers/gpu/drm/i915/i915_drv.h

@@ -1901,14 +1901,6 @@ struct drm_i915_private {
 		ktime_t last_init_time;
 
 		struct i915_vma *scratch;
-
-		/*
-		 * We must never wait on the GPU while holding a lock as we
-		 * may need to perform a GPU reset. So while we don't need to
-		 * serialise wait/reset with an explicit lock, we do want
-		 * lockdep to detect potential dependency cycles.
-		 */
-		struct lockdep_map reset_lockmap;
 	} gt;
 
 	struct {

drivers/gpu/drm/i915/i915_gem.c

@@ -1746,7 +1746,6 @@ static void i915_gem_init__mm(struct drm_i915_private *i915)
 
 int i915_gem_init_early(struct drm_i915_private *dev_priv)
 {
-	static struct lock_class_key reset_key;
 	int err;
 
 	intel_gt_pm_init(dev_priv);
@@ -1754,8 +1753,6 @@ int i915_gem_init_early(struct drm_i915_private *dev_priv)
 	INIT_LIST_HEAD(&dev_priv->gt.active_rings);
 	INIT_LIST_HEAD(&dev_priv->gt.closed_vma);
 	spin_lock_init(&dev_priv->gt.closed_lock);
-	lockdep_init_map(&dev_priv->gt.reset_lockmap,
-			 "i915.reset", &reset_key, 0);
 
 	i915_gem_init__mm(dev_priv);
 	i915_gem_init__pm(dev_priv);

drivers/gpu/drm/i915/i915_request.c

@@ -1444,7 +1444,15 @@ long i915_request_wait(struct i915_request *rq,
 		return -ETIME;
 
 	trace_i915_request_wait_begin(rq, flags);
-	lock_map_acquire(&rq->i915->gt.reset_lockmap);
+
+	/*
+	 * We must never wait on the GPU while holding a lock as we
+	 * may need to perform a GPU reset. So while we don't need to
+	 * serialise wait/reset with an explicit lock, we do want
+	 * lockdep to detect potential dependency cycles.
+	 */
+	mutex_acquire(&rq->i915->gpu_error.wedge_mutex.dep_map,
+		      0, 0, _THIS_IP_);
 
 	/*
 	 * Optimistic spin before touching IRQs.
@@ -1520,7 +1528,7 @@ long i915_request_wait(struct i915_request *rq,
 	dma_fence_remove_callback(&rq->fence, &wait.cb);
 
 out:
-	lock_map_release(&rq->i915->gt.reset_lockmap);
+	mutex_release(&rq->i915->gpu_error.wedge_mutex.dep_map, 0, _THIS_IP_);
 	trace_i915_request_wait_end(rq);
 	return timeout;
 }

drivers/gpu/drm/i915/selftests/mock_gem_device.c

@@ -130,7 +130,6 @@ static struct dev_pm_domain pm_domain = {
 
 struct drm_i915_private *mock_gem_device(void)
 {
-	static struct lock_class_key reset_key;
 	struct drm_i915_private *i915;
 	struct pci_dev *pdev;
 	int err;
@@ -205,7 +204,6 @@ struct drm_i915_private *mock_gem_device(void)
 	INIT_LIST_HEAD(&i915->gt.active_rings);
 	INIT_LIST_HEAD(&i915->gt.closed_vma);
 	spin_lock_init(&i915->gt.closed_lock);
-	lockdep_init_map(&i915->gt.reset_lockmap, "i915.reset", &reset_key, 0);
 
 	mutex_lock(&i915->drm.struct_mutex);