[PATCH 27/29] drm/i915: Convert fences to use a GGTT lock rather than struct_mutex

Chris Wilson chris at chris-wilson.co.uk
Sat Jun 23 17:18:59 UTC 2018


Introduce a new mutex to guard all of the vma operations within a vm (as
opposed to the BKL struct_mutex) and start by using it to guard the
fence operations for a GGTT VMA.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_debugfs.c        |  2 +-
 drivers/gpu/drm/i915/i915_gem.c            | 13 ++++-
 drivers/gpu/drm/i915/i915_gem_execbuffer.c |  5 +-
 drivers/gpu/drm/i915/i915_gem_fence_reg.c  | 68 +++++++++++++++++-----
 drivers/gpu/drm/i915/i915_vma.c            | 12 ++--
 drivers/gpu/drm/i915/i915_vma.h            | 23 +++++++-
 6 files changed, 95 insertions(+), 28 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 1511d6db626d..d2c8e9edd0d5 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -80,7 +80,7 @@ static char get_tiling_flag(struct drm_i915_gem_object *obj)
 
 static char get_global_flag(struct drm_i915_gem_object *obj)
 {
-	return obj->userfault_count ? 'g' : ' ';
+	return READ_ONCE(obj->userfault_count) ? 'g' : ' ';
 }
 
 static char get_pin_mapped_flag(struct drm_i915_gem_object *obj)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 3d80fe9a6669..eec08d9b7af2 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2081,12 +2081,14 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
 		goto err_fence;
 
 	/* Mark as being mmapped into userspace for later revocation */
+	mutex_lock(&vma->vm->mutex);
 	assert_rpm_wakelock_held(dev_priv);
 	if (!i915_vma_set_userfault(vma) && !obj->userfault_count++)
 		list_add(&obj->userfault_link, &dev_priv->mm.userfault_list);
 	GEM_BUG_ON(!obj->userfault_count);
 
 	i915_vma_set_ggtt_write(vma);
+	mutex_unlock(&vma->vm->mutex);
 
 err_fence:
 	i915_vma_unpin_fence(vma);
@@ -2176,8 +2178,8 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 	 * requirement that operations to the GGTT be made holding the RPM
 	 * wakeref.
 	 */
-	lockdep_assert_held(&i915->drm.struct_mutex);
 	intel_runtime_pm_get(i915);
+	mutex_lock(&i915->ggtt.vm.mutex);
 
 	if (!obj->userfault_count)
 		goto out;
@@ -2194,6 +2196,7 @@ i915_gem_release_mmap(struct drm_i915_gem_object *obj)
 	wmb();
 
 out:
+	mutex_unlock(&i915->ggtt.vm.mutex);
 	intel_runtime_pm_put(i915);
 }
 
@@ -2206,10 +2209,12 @@ void i915_gem_runtime_suspend(struct drm_i915_private *i915)
 	/*
 	 * Only called during RPM suspend. All users of the userfault_list
 	 * must be holding an RPM wakeref to ensure that this can not
-	 * run concurrently with themselves (and use the struct_mutex for
+	 * run concurrently with themselves (and use the ggtt->mutex for
 	 * protection between themselves).
 	 */
 
+	mutex_lock(&i915->ggtt.vm.mutex);
+
 	list_for_each_entry_safe(obj, on,
 				 &i915->mm.userfault_list, userfault_link)
 		__i915_gem_object_release_mmap(obj);
@@ -2238,6 +2243,8 @@ void i915_gem_runtime_suspend(struct drm_i915_private *i915)
 		GEM_BUG_ON(i915_vma_has_userfault(reg->vma));
 		reg->dirty = true;
 	}
+
+	mutex_unlock(&i915->ggtt.vm.mutex);
 }
 
 static int i915_gem_object_create_mmap_offset(struct drm_i915_gem_object *obj)
@@ -4866,7 +4873,7 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
 		mutex_unlock(&i915->drm.struct_mutex);
 
 		GEM_BUG_ON(obj->bind_count);
-		GEM_BUG_ON(obj->userfault_count);
+		GEM_BUG_ON(READ_ONCE(obj->userfault_count));
 		GEM_BUG_ON(atomic_read(&obj->frontbuffer_bits));
 		GEM_BUG_ON(!list_empty(&obj->lut_list));
 
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 8bbbc8e5fb86..c25b7b63f3f1 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -426,8 +426,11 @@ static inline void __eb_unreserve_vma(struct i915_vma *vma, unsigned int flags)
 {
 	GEM_BUG_ON(!(flags & __EXEC_OBJECT_HAS_PIN));
 
-	if (unlikely(flags & __EXEC_OBJECT_HAS_FENCE))
+	if (unlikely(flags & __EXEC_OBJECT_HAS_FENCE)) {
+		mutex_lock(&vma->vm->mutex);
 		__i915_vma_unpin_fence(vma);
+		mutex_unlock(&vma->vm->mutex);
+	}
 
 	__i915_vma_unpin(vma);
 }
diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
index 60fa5a8276cb..9313a8e675c8 100644
--- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c
+++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c
@@ -188,6 +188,8 @@ static void i830_write_fence_reg(struct drm_i915_fence_reg *fence,
 static void fence_write(struct drm_i915_fence_reg *fence,
 			struct i915_vma *vma)
 {
+	lockdep_assert_held(&fence->ggtt->vm.mutex);
+
 	/* Previous access through the fence register is marshalled by
 	 * the mb() inside the fault handlers (i915_gem_release_mmaps)
 	 * and explicitly managed for internal users.
@@ -213,6 +215,8 @@ static int fence_update(struct drm_i915_fence_reg *fence,
 	struct i915_ggtt *ggtt = fence->ggtt;
 	int ret;
 
+	lockdep_assert_held(&ggtt->vm.mutex);
+
 	if (vma) {
 		if (!i915_vma_is_map_and_fenceable(vma))
 			return -EINVAL;
@@ -289,14 +293,39 @@ static int fence_update(struct drm_i915_fence_reg *fence,
 int i915_vma_put_fence(struct i915_vma *vma)
 {
 	struct drm_i915_fence_reg *fence = vma->fence;
+	int err;
 
 	if (!fence)
 		return 0;
 
-	if (fence->pin_count)
-		return -EBUSY;
+	mutex_lock(&vma->vm->mutex);
+	if (!fence->pin_count)
+		err = fence_update(fence, NULL);
+	else
+		err = -EBUSY;
+	mutex_unlock(&vma->vm->mutex);
 
-	return fence_update(fence, NULL);
+	return err;
+}
+
+void i915_vma_revoke_fence(struct i915_vma *vma)
+{
+	struct drm_i915_fence_reg *fence;
+
+	GEM_BUG_ON(!i915_vma_is_ggtt(vma));
+	lockdep_assert_held(&vma->vm->mutex);
+
+	fence = vma->fence;
+	if (!fence)
+		return;
+
+	GEM_BUG_ON(fence->pin_count);
+
+	list_move(&fence->link, &i915_vm_to_ggtt(vma->vm)->fence_list);
+	vma->fence = NULL;
+
+	fence_write(fence, NULL);
+	fence->vma = NULL;
 }
 
 static struct drm_i915_fence_reg *fence_find(struct i915_ggtt *ggtt)
@@ -337,8 +366,7 @@ static struct drm_i915_fence_reg *fence_find(struct i915_ggtt *ggtt)
  *
  * 0 on success, negative error code on failure.
  */
-int
-i915_vma_pin_fence(struct i915_vma *vma)
+int __i915_vma_pin_fence(struct i915_vma *vma)
 {
 	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vma->vm);
 	struct i915_vma *set = i915_gem_object_is_tiled(vma->obj) ? vma : NULL;
@@ -349,6 +377,7 @@ i915_vma_pin_fence(struct i915_vma *vma)
 	 * must keep the device awake whilst using the fence.
 	 */
 	assert_rpm_wakelock_held(ggtt->vm.i915);
+	lockdep_assert_held(&ggtt->vm.mutex);
 
 	/* Just update our place in the LRU if our fence is getting reused. */
 	if (vma->fence) {
@@ -399,27 +428,34 @@ i915_reserve_fence(struct drm_i915_private *i915)
 	int count;
 	int ret;
 
-	lockdep_assert_held(&i915->drm.struct_mutex);
+	mutex_lock(&i915->ggtt.vm.mutex);
 
 	/* Keep at least one fence available for the display engine. */
 	count = 0;
 	list_for_each_entry(fence, &ggtt->fence_list, link)
 		count += !fence->pin_count;
-	if (count <= 1)
-		return ERR_PTR(-ENOSPC);
+	if (count <= 1) {
+		fence = ERR_PTR(-ENOSPC);
+		goto out_unlock;
+	}
 
 	fence = fence_find(ggtt);
 	if (IS_ERR(fence))
-		return fence;
+		goto out_unlock;
 
 	if (fence->vma) {
 		/* Force-remove fence from VMA */
 		ret = fence_update(fence, NULL);
-		if (ret)
-			return ERR_PTR(ret);
+		if (ret) {
+			fence = ERR_PTR(ret);
+			goto out_unlock;
+		}
 	}
 
 	list_del(&fence->link);
+
+out_unlock:
+	mutex_unlock(&i915->ggtt.vm.mutex);
 	return fence;
 }
 
@@ -431,9 +467,9 @@ i915_reserve_fence(struct drm_i915_private *i915)
  */
 void i915_unreserve_fence(struct drm_i915_fence_reg *fence)
 {
-	lockdep_assert_held(&fence->ggtt->vm.i915->drm.struct_mutex);
-
+	mutex_lock(&fence->ggtt->vm.mutex);
 	list_add(&fence->link, &fence->ggtt->fence_list);
+	mutex_unlock(&fence->ggtt->vm.mutex);
 }
 
 /**
@@ -451,8 +487,7 @@ void i915_gem_revoke_fences(struct drm_i915_private *i915)
 	struct i915_ggtt *ggtt = &i915->ggtt;
 	int i;
 
-	lockdep_assert_held(&i915->drm.struct_mutex);
-
+	mutex_lock(&ggtt->vm.mutex);
 	for (i = 0; i < ggtt->num_fence_regs; i++) {
 		struct drm_i915_fence_reg *fence = &ggtt->fence_regs[i];
 
@@ -461,6 +496,7 @@ void i915_gem_revoke_fences(struct drm_i915_private *i915)
 		if (fence->vma)
 			i915_vma_revoke_mmap(fence->vma);
 	}
+	mutex_unlock(&ggtt->vm.mutex);
 }
 
 /**
@@ -476,6 +512,7 @@ void i915_gem_restore_fences(struct drm_i915_private *i915)
 	struct i915_ggtt *ggtt = &i915->ggtt;
 	int i;
 
+	mutex_lock(&ggtt->vm.mutex);
 	for (i = 0; i < ggtt->num_fence_regs; i++) {
 		struct drm_i915_fence_reg *reg = &ggtt->fence_regs[i];
 		struct i915_vma *vma = reg->vma;
@@ -498,6 +535,7 @@ void i915_gem_restore_fences(struct drm_i915_private *i915)
 		fence_write(reg, vma);
 		reg->vma = vma;
 	}
+	mutex_unlock(&ggtt->vm.mutex);
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index db1b0939a934..20a524e1876e 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -833,7 +833,7 @@ void i915_vma_revoke_mmap(struct i915_vma *vma)
 	struct drm_vma_offset_node *node = &vma->obj->base.vma_node;
 	u64 vma_offset;
 
-	lockdep_assert_held(&vma->vm->i915->drm.struct_mutex);
+	lockdep_assert_held(&vma->vm->mutex);
 
 	if (!i915_vma_has_userfault(vma))
 		return;
@@ -1035,6 +1035,8 @@ int i915_vma_unbind(struct i915_vma *vma)
 		return 0;
 
 	if (i915_vma_is_map_and_fenceable(vma)) {
+		mutex_lock(&vma->vm->mutex);
+
 		/*
 		 * Check that we have flushed all writes through the GGTT
 		 * before the unbind, other due to non-strict nature of those
@@ -1044,16 +1046,14 @@ int i915_vma_unbind(struct i915_vma *vma)
 		i915_vma_flush_writes(vma);
 		GEM_BUG_ON(i915_vma_has_ggtt_write(vma));
 
-		/* release the fence reg _after_ flushing */
-		ret = i915_vma_put_fence(vma);
-		if (ret)
-			return ret;
-
 		/* Force a pagefault for domain tracking on next user access */
 		i915_vma_revoke_mmap(vma);
+		i915_vma_revoke_fence(vma);
 
 		__i915_vma_iounmap(vma);
 		vma->flags &= ~I915_VMA_CAN_FENCE;
+
+		mutex_unlock(&vma->vm->mutex);
 	}
 	GEM_BUG_ON(vma->fence);
 	GEM_BUG_ON(i915_vma_has_userfault(vma));
diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
index 1d3080603a18..0af82ff98da7 100644
--- a/drivers/gpu/drm/i915/i915_vma.h
+++ b/drivers/gpu/drm/i915/i915_vma.h
@@ -190,6 +190,7 @@ static inline bool i915_vma_set_userfault(struct i915_vma *vma)
 
 static inline void i915_vma_unset_userfault(struct i915_vma *vma)
 {
+	lockdep_assert_held(&vma->vm->mutex);
 	return __clear_bit(I915_VMA_USERFAULT_BIT, &vma->flags);
 }
 
@@ -378,11 +379,26 @@ static inline struct page *i915_vma_first_page(struct i915_vma *vma)
  *
  * True if the vma has a fence, false otherwise.
  */
-int i915_vma_pin_fence(struct i915_vma *vma);
+int __i915_vma_pin_fence(struct i915_vma *vma);
+static inline int i915_vma_pin_fence(struct i915_vma *vma)
+{
+	int err;
+
+	mutex_lock(&vma->vm->mutex);
+	err = __i915_vma_pin_fence(vma);
+	mutex_unlock(&vma->vm->mutex);
+
+	return err;
+}
+
 int __must_check i915_vma_put_fence(struct i915_vma *vma);
+void i915_vma_revoke_fence(struct i915_vma *vma);
 
 static inline void __i915_vma_unpin_fence(struct i915_vma *vma)
 {
+	lockdep_assert_held(&vma->vm->mutex);
+	GEM_BUG_ON(!i915_vma_is_ggtt(vma));
+
 	GEM_BUG_ON(vma->fence->pin_count <= 0);
 	vma->fence->pin_count--;
 }
@@ -399,8 +415,11 @@ static inline void
 i915_vma_unpin_fence(struct i915_vma *vma)
 {
 	/* lockdep_assert_held(&vma->vm->i915->drm.struct_mutex); */
-	if (vma->fence)
+	if (vma->fence) {
+		mutex_lock(&vma->vm->mutex);
 		__i915_vma_unpin_fence(vma);
+		mutex_unlock(&vma->vm->mutex);
+	}
 }
 
 void i915_vma_parked(struct drm_i915_private *i915);
-- 
2.18.0



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