On Sun, Dec 22, 2019 at 09:02:55PM +0000, Chris Wilson wrote:
> Start introducing a kref on i915_vma in order to protect the vma unbind
> from a parallel destruction. Later, we will use the refcount to manage
> all access.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
The patchset got rid of the vma unbind/destroy race I could repro with
kms_plane:
Tested-and-acked-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gem/i915_gem_object.c | 2 +-
> .../gpu/drm/i915/gem/selftests/huge_pages.c | 3 +--
> .../drm/i915/gem/selftests/i915_gem_mman.c | 4 +--
> drivers/gpu/drm/i915/i915_gem.c | 27 +++++++------------
> drivers/gpu/drm/i915/i915_gem_gtt.c | 5 ++--
> drivers/gpu/drm/i915/i915_vma.c | 9 ++++---
> drivers/gpu/drm/i915/i915_vma.h | 25 ++++++++++++++---
> 7 files changed, 44 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index ddc82a7a34ff..46bacc82ddc4 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -194,7 +194,7 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
> GEM_BUG_ON(vma->obj != obj);
> spin_unlock(&obj->vma.lock);
>
> - i915_vma_destroy(vma);
> + __i915_vma_put(vma);
>
> spin_lock(&obj->vma.lock);
> }
> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> index 497c367a79ca..2479395c1873 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> @@ -1110,8 +1110,7 @@ static int __igt_write_huge(struct intel_context *ce,
> out_vma_unpin:
> i915_vma_unpin(vma);
> out_vma_close:
> - i915_vma_destroy(vma);
> -
> + __i915_vma_put(vma);
> return err;
> }
>
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
> index 591435c5f368..cbf796da64e3 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
> @@ -163,7 +163,7 @@ static int check_partial_mapping(struct drm_i915_gem_object *obj,
> kunmap(p);
>
> out:
> - i915_vma_destroy(vma);
> + __i915_vma_put(vma);
> return err;
> }
>
> @@ -257,7 +257,7 @@ static int check_partial_mappings(struct drm_i915_gem_object *obj,
> if (err)
> return err;
>
> - i915_vma_destroy(vma);
> + __i915_vma_put(vma);
>
> if (igt_timeout(end_time,
> "%s: timed out after tiling=%d stride=%d\n",
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index e9f82e9cb6ff..9ddcf17230e6 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -136,7 +136,6 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
> struct i915_vma,
> obj_link))) {
> struct i915_address_space *vm = vma->vm;
> - bool awake = false;
>
> list_move_tail(&vma->obj_link, &still_in_list);
> if (!i915_vma_is_bound(vma, I915_VMA_BIND_MASK))
> @@ -147,26 +146,18 @@ int i915_gem_object_unbind(struct drm_i915_gem_object *obj,
> break;
>
> /* Prevent vma being freed by i915_vma_parked as we unbind */
> - if (intel_gt_pm_get_if_awake(vm->gt)) {
> - awake = true;
> - } else {
> - if (i915_vma_is_closed(vma)) {
> - spin_unlock(&obj->vma.lock);
> - i915_vma_parked(vm->gt);
> - goto err_vm;
> - }
> - }
> -
> + vma = __i915_vma_get(vma);
> spin_unlock(&obj->vma.lock);
>
> - ret = -EBUSY;
> - if (flags & I915_GEM_OBJECT_UNBIND_ACTIVE ||
> - !i915_vma_is_active(vma))
> - ret = i915_vma_unbind(vma);
> + if (vma) {
> + ret = -EBUSY;
> + if (flags & I915_GEM_OBJECT_UNBIND_ACTIVE ||
> + !i915_vma_is_active(vma))
> + ret = i915_vma_unbind(vma);
> +
> + __i915_vma_put(vma);
> + }
>
> - if (awake)
> - intel_gt_pm_put(vm->gt);
> -err_vm:
> i915_vm_close(vm);
> spin_lock(&obj->vma.lock);
> }
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index 2ad2fc5efdbf..1efe58ad0ce9 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -534,7 +534,7 @@ void __i915_vm_close(struct i915_address_space *vm)
>
> atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
> WARN_ON(__i915_vma_unbind(vma));
> - i915_vma_destroy(vma);
> + __i915_vma_put(vma);
>
> i915_gem_object_put(obj);
> }
> @@ -1812,7 +1812,7 @@ static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
> {
> struct gen6_ppgtt *ppgtt = to_gen6_ppgtt(i915_vm_to_ppgtt(vm));
>
> - i915_vma_destroy(ppgtt->vma);
> + __i915_vma_put(ppgtt->vma);
>
> gen6_ppgtt_free_pd(ppgtt);
> free_scratch(vm);
> @@ -1895,6 +1895,7 @@ static struct i915_vma *pd_vma_create(struct gen6_ppgtt *ppgtt, int size)
>
> i915_active_init(&vma->active, NULL, NULL);
>
> + kref_init(&vma->ref);
> mutex_init(&vma->pages_mutex);
> vma->vm = i915_vm_get(&ggtt->vm);
> vma->ops = &pd_vma_ops;
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index f3ac837ba3b3..cbd783c31adb 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -114,6 +114,7 @@ vma_create(struct drm_i915_gem_object *obj,
> if (vma == NULL)
> return ERR_PTR(-ENOMEM);
>
> + kref_init(&vma->ref);
> mutex_init(&vma->pages_mutex);
> vma->vm = i915_vm_get(vm);
> vma->ops = &vm->vma_ops;
> @@ -1021,8 +1022,10 @@ void i915_vma_reopen(struct i915_vma *vma)
> __i915_vma_remove_closed(vma);
> }
>
> -void i915_vma_destroy(struct i915_vma *vma)
> +void i915_vma_release(struct kref *ref)
> {
> + struct i915_vma *vma = container_of(ref, typeof(*vma), ref);
> +
> if (drm_mm_node_allocated(&vma->node)) {
> mutex_lock(&vma->vm->mutex);
> atomic_and(~I915_VMA_PIN_MASK, &vma->flags);
> @@ -1072,7 +1075,7 @@ void i915_vma_parked(struct intel_gt *gt)
> spin_unlock_irq(>->closed_lock);
>
> if (obj) {
> - i915_vma_destroy(vma);
> + __i915_vma_put(vma);
> i915_gem_object_put(obj);
> }
>
> @@ -1236,7 +1239,7 @@ int __i915_vma_unbind(struct i915_vma *vma)
> i915_vma_detach(vma);
> vma_unbind_pages(vma);
>
> - drm_mm_remove_node(&vma->node); /* pairs with i915_vma_destroy() */
> + drm_mm_remove_node(&vma->node); /* pairs with i915_vma_release() */
> return 0;
> }
>
> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
> index 0e0b61c24551..5fffa3c58908 100644
> --- a/drivers/gpu/drm/i915/i915_vma.h
> +++ b/drivers/gpu/drm/i915/i915_vma.h
> @@ -51,14 +51,19 @@ enum i915_cache_level;
> */
> struct i915_vma {
> struct drm_mm_node node;
> - struct drm_i915_gem_object *obj;
> +
> struct i915_address_space *vm;
> const struct i915_vma_ops *ops;
> - struct i915_fence_reg *fence;
> +
> + struct drm_i915_gem_object *obj;
> struct dma_resv *resv; /** Alias of obj->resv */
> +
> struct sg_table *pages;
> void __iomem *iomap;
> void *private; /* owned by creator */
> +
> + struct i915_fence_reg *fence;
> +
> u64 size;
> u64 display_alignment;
> struct i915_page_sizes page_sizes;
> @@ -74,6 +79,7 @@ struct i915_vma {
> * handles (but same file) for execbuf, i.e. the number of aliases
> * that exist in the ctx->handle_vmas LUT for this vma.
> */
> + struct kref ref;
> atomic_t open_count;
> atomic_t flags;
> /**
> @@ -336,7 +342,20 @@ int __must_check i915_vma_unbind(struct i915_vma *vma);
> void i915_vma_unlink_ctx(struct i915_vma *vma);
> void i915_vma_close(struct i915_vma *vma);
> void i915_vma_reopen(struct i915_vma *vma);
> -void i915_vma_destroy(struct i915_vma *vma);
> +
> +static inline struct i915_vma *__i915_vma_get(struct i915_vma *vma)
> +{
> + if (kref_get_unless_zero(&vma->ref))
> + return vma;
> +
> + return NULL;
> +}
> +
> +void i915_vma_release(struct kref *ref);
> +static inline void __i915_vma_put(struct i915_vma *vma)
> +{
> + kref_put(&vma->ref, i915_vma_release);
> +}
>
> #define assert_vma_held(vma) dma_resv_assert_held((vma)->resv)
>
> --
> 2.24.1
>
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