[Intel-gfx] [PATCH 04/26] drm/i915: Add an implementation for i915_gem_ww_ctx locking, v2.

Tvrtko Ursulin tvrtko.ursulin at linux.intel.com
Mon Jun 29 12:32:16 UTC 2020


On 23/06/2020 15:28, Maarten Lankhorst wrote:
> i915_gem_ww_ctx is used to lock all gem bo's for pinning and memory
> eviction. We don't use it yet, but lets start adding the definition
> first.
> 
> To use it, we have to pass a non-NULL ww to gem_object_lock, and don't
> unlock directly. It is done in i915_gem_ww_ctx_fini.
> 
> Changes since v1:
> - Change ww_ctx and obj order in locking functions (Jonas Lahtinen)
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_display.c  |  4 +-
>   .../gpu/drm/i915/gem/i915_gem_client_blt.c    |  2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_context.c   |  2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c    |  4 +-
>   drivers/gpu/drm/i915/gem/i915_gem_domain.c    | 10 ++--
>   .../gpu/drm/i915/gem/i915_gem_execbuffer.c    |  4 +-
>   drivers/gpu/drm/i915/gem/i915_gem_object.c    |  2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_object.h    | 38 +++++++++++---
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |  9 ++++
>   drivers/gpu/drm/i915/gem/i915_gem_pm.c        |  2 +-
>   drivers/gpu/drm/i915/gem/i915_gem_tiling.c    |  2 +-
>   .../gpu/drm/i915/gem/selftests/huge_pages.c   |  2 +-
>   .../i915/gem/selftests/i915_gem_client_blt.c  |  2 +-
>   .../i915/gem/selftests/i915_gem_coherency.c   | 10 ++--
>   .../drm/i915/gem/selftests/i915_gem_context.c |  4 +-
>   .../drm/i915/gem/selftests/i915_gem_mman.c    |  4 +-
>   .../drm/i915/gem/selftests/i915_gem_phys.c    |  2 +-
>   .../gpu/drm/i915/gt/selftest_workarounds.c    |  2 +-
>   drivers/gpu/drm/i915/gvt/cmd_parser.c         |  2 +-
>   drivers/gpu/drm/i915/i915_gem.c               | 52 +++++++++++++++++--
>   drivers/gpu/drm/i915/i915_gem.h               | 11 ++++
>   drivers/gpu/drm/i915/selftests/i915_gem.c     | 41 +++++++++++++++
>   drivers/gpu/drm/i915/selftests/i915_vma.c     |  2 +-
>   .../drm/i915/selftests/intel_memory_region.c  |  2 +-
>   24 files changed, 173 insertions(+), 42 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 7457813ef273..e909ccc37a54 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -2309,7 +2309,7 @@ intel_pin_and_fence_fb_obj(struct drm_framebuffer *fb,
>   
>   void intel_unpin_fb_vma(struct i915_vma *vma, unsigned long flags)
>   {
> -	i915_gem_object_lock(vma->obj);
> +	i915_gem_object_lock(vma->obj, NULL);
>   	if (flags & PLANE_HAS_FENCE)
>   		i915_vma_unpin_fence(vma);
>   	i915_gem_object_unpin_from_display_plane(vma);
> @@ -17112,7 +17112,7 @@ static int intel_framebuffer_init(struct intel_framebuffer *intel_fb,
>   	if (!intel_fb->frontbuffer)
>   		return -ENOMEM;
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	tiling = i915_gem_object_get_tiling(obj);
>   	stride = i915_gem_object_get_stride(obj);
>   	i915_gem_object_unlock(obj);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> index d3a86a4d5c04..c182091c00ff 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_client_blt.c
> @@ -286,7 +286,7 @@ int i915_gem_schedule_fill_pages_blt(struct drm_i915_gem_object *obj,
>   	dma_fence_init(&work->dma, &clear_pages_work_ops, &fence_lock, 0, 0);
>   	i915_sw_fence_init(&work->wait, clear_pages_work_notify);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_sw_fence_await_reservation(&work->wait,
>   					      obj->base.resv, NULL, true, 0,
>   					      I915_FENCE_GFP);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> index 30c229fcb404..a996583640ee 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
> @@ -113,7 +113,7 @@ static void lut_close(struct i915_gem_context *ctx)
>   			continue;
>   
>   		rcu_read_unlock();
> -		i915_gem_object_lock(obj);
> +		i915_gem_object_lock(obj, NULL);
>   		list_for_each_entry(lut, &obj->lut_list, obj_link) {
>   			if (lut->ctx != ctx)
>   				continue;
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> index 2679380159fc..27fddc22a7c6 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> @@ -128,7 +128,7 @@ static int i915_gem_begin_cpu_access(struct dma_buf *dma_buf, enum dma_data_dire
>   	if (err)
>   		return err;
>   
> -	err = i915_gem_object_lock_interruptible(obj);
> +	err = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (err)
>   		goto out;
>   
> @@ -149,7 +149,7 @@ static int i915_gem_end_cpu_access(struct dma_buf *dma_buf, enum dma_data_direct
>   	if (err)
>   		return err;
>   
> -	err = i915_gem_object_lock_interruptible(obj);
> +	err = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (err)
>   		goto out;
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> index 7f76fc68f498..c0acfc97fae3 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> @@ -32,7 +32,7 @@ void i915_gem_object_flush_if_display(struct drm_i915_gem_object *obj)
>   	if (!i915_gem_object_is_framebuffer(obj))
>   		return;
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	__i915_gem_object_flush_for_display(obj);
>   	i915_gem_object_unlock(obj);
>   }
> @@ -197,7 +197,7 @@ int i915_gem_object_set_cache_level(struct drm_i915_gem_object *obj,
>   	if (ret)
>   		return ret;
>   
> -	ret = i915_gem_object_lock_interruptible(obj);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		return ret;
>   
> @@ -536,7 +536,7 @@ i915_gem_set_domain_ioctl(struct drm_device *dev, void *data,
>   	if (err)
>   		goto out;
>   
> -	err = i915_gem_object_lock_interruptible(obj);
> +	err = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (err)
>   		goto out_unpin;
>   
> @@ -576,7 +576,7 @@ int i915_gem_object_prepare_read(struct drm_i915_gem_object *obj,
>   	if (!i915_gem_object_has_struct_page(obj))
>   		return -ENODEV;
>   
> -	ret = i915_gem_object_lock_interruptible(obj);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		return ret;
>   
> @@ -630,7 +630,7 @@ int i915_gem_object_prepare_write(struct drm_i915_gem_object *obj,
>   	if (!i915_gem_object_has_struct_page(obj))
>   		return -ENODEV;
>   
> -	ret = i915_gem_object_lock_interruptible(obj);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		return ret;
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 2b4c210638c1..391d22051b20 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -813,7 +813,7 @@ static int __eb_add_lut(struct i915_execbuffer *eb,
>   		if (err == 0) { /* And nor has this handle */
>   			struct drm_i915_gem_object *obj = vma->obj;
>   
> -			i915_gem_object_lock(obj);
> +			i915_gem_object_lock(obj, NULL);
>   			if (idr_find(&eb->file->object_idr, handle) == obj) {
>   				list_add(&lut->obj_link, &obj->lut_list);
>   			} else {
> @@ -1083,7 +1083,7 @@ static void *reloc_iomap(struct drm_i915_gem_object *obj,
>   		if (use_cpu_reloc(cache, obj))
>   			return NULL;
>   
> -		i915_gem_object_lock(obj);
> +		i915_gem_object_lock(obj, NULL);
>   		err = i915_gem_object_set_to_gtt_domain(obj, true);
>   		i915_gem_object_unlock(obj);
>   		if (err)
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index b6ec5b50d93b..b59e2d40c347 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -108,7 +108,7 @@ void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file)
>   	struct i915_lut_handle *lut, *ln;
>   	LIST_HEAD(close);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	list_for_each_entry_safe(lut, ln, &obj->lut_list, obj_link) {
>   		struct i915_gem_context *ctx = lut->ctx;
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index 2faa481cc18f..5103067269b0 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -110,20 +110,44 @@ i915_gem_object_put(struct drm_i915_gem_object *obj)
>   
>   #define assert_object_held(obj) dma_resv_assert_held((obj)->base.resv)
>   
> -static inline void i915_gem_object_lock(struct drm_i915_gem_object *obj)
> +static inline int __i915_gem_object_lock(struct drm_i915_gem_object *obj,
> +					 struct i915_gem_ww_ctx *ww,
> +					 bool intr)
>   {
> -	dma_resv_lock(obj->base.resv, NULL);
> +	int ret;
> +
> +	if (intr)
> +		ret = dma_resv_lock_interruptible(obj->base.resv, ww ? &ww->ctx : NULL);
> +	else
> +		ret = dma_resv_lock(obj->base.resv, ww ? &ww->ctx : NULL);
> +
> +	if (!ret && ww)
> +		list_add_tail(&obj->obj_link, &ww->obj_list);
> +	if (ret == -EALREADY)
> +		ret = 0;
> +
> +	if (ret == -EDEADLK)
> +		ww->contended = obj;
> +
> +	return ret;

Feels a bit on the large side for inline now, no? Quite a few 
conditionals. Or you are counting on compiler optimisation because ww 
and intr are passed in as mostly const?

>   }
>   
> -static inline bool i915_gem_object_trylock(struct drm_i915_gem_object *obj)
> +static inline int i915_gem_object_lock(struct drm_i915_gem_object *obj,
> +				       struct i915_gem_ww_ctx *ww)
>   {
> -	return dma_resv_trylock(obj->base.resv);
> +	return __i915_gem_object_lock(obj, ww, ww && ww->intr);
>   }
>   
> -static inline int
> -i915_gem_object_lock_interruptible(struct drm_i915_gem_object *obj)
> +static inline int i915_gem_object_lock_interruptible(struct drm_i915_gem_object *obj,
> +						     struct i915_gem_ww_ctx *ww)
>   {
> -	return dma_resv_lock_interruptible(obj->base.resv, NULL);
> +	WARN_ON(ww && !ww->intr);
> +	return __i915_gem_object_lock(obj, ww, true);

I see that ww->intr is set at ctx init time. At what times it is 
expected that the individual lock calls would override that?

> +}
> +
> +static inline bool i915_gem_object_trylock(struct drm_i915_gem_object *obj)
> +{
> +	return dma_resv_trylock(obj->base.resv);
>   }
>   
>   static inline void i915_gem_object_unlock(struct drm_i915_gem_object *obj)
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> index b1f82a11aef2..3740c0080e38 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -122,6 +122,15 @@ struct drm_i915_gem_object {
>   	 */
>   	struct list_head lut_list;
>   
> +	/**
> +	 * @obj_link: Link into @i915_gem_ww_ctx.obj_list
> +	 *
> +	 * When we lock this object through i915_gem_object_lock() with a
> +	 * context, we add it to the list to ensure we can unlock everything
> +	 * when i915_gem_ww_ctx_backoff() or i915_gem_ww_ctx_fini() are called.
> +	 */
> +	struct list_head obj_link;
> +
>   	/** Stolen memory for this object, instead of being backed by shmem. */
>   	struct drm_mm_node *stolen;
>   	union {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
> index 3d215164dd5a..40d3e40500fa 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_pm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_pm.c
> @@ -84,7 +84,7 @@ void i915_gem_suspend_late(struct drm_i915_private *i915)
>   
>   			spin_unlock_irqrestore(&i915->mm.obj_lock, flags);
>   
> -			i915_gem_object_lock(obj);
> +			i915_gem_object_lock(obj, NULL);
>   			drm_WARN_ON(&i915->drm,
>   			    i915_gem_object_set_to_gtt_domain(obj, false));
>   			i915_gem_object_unlock(obj);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> index 0158e49bf9bb..65fbf29c4852 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_tiling.c
> @@ -249,7 +249,7 @@ i915_gem_object_set_tiling(struct drm_i915_gem_object *obj,
>   	 * whilst executing a fenced command for an untiled object.
>   	 */
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	if (i915_gem_object_is_framebuffer(obj)) {
>   		i915_gem_object_unlock(obj);
>   		return -EBUSY;
> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> index 8291ede6902c..eb2011ccb92b 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> @@ -947,7 +947,7 @@ static int gpu_write(struct intel_context *ce,
>   {
>   	int err;
>   
> -	i915_gem_object_lock(vma->obj);
> +	i915_gem_object_lock(vma->obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(vma->obj, true);
>   	i915_gem_object_unlock(vma->obj);
>   	if (err)
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
> index 299c29e9ad86..4e36d4897ea6 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_client_blt.c
> @@ -75,7 +75,7 @@ static int __igt_client_fill(struct intel_engine_cs *engine)
>   		if (err)
>   			goto err_unpin;
>   
> -		i915_gem_object_lock(obj);
> +		i915_gem_object_lock(obj, NULL);
>   		err = i915_gem_object_set_to_cpu_domain(obj, false);
>   		i915_gem_object_unlock(obj);
>   		if (err)
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
> index 87d7d8aa080f..1de2959b153c 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
> @@ -82,7 +82,7 @@ static int gtt_set(struct context *ctx, unsigned long offset, u32 v)
>   	u32 __iomem *map;
>   	int err = 0;
>   
> -	i915_gem_object_lock(ctx->obj);
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(ctx->obj, true);
>   	i915_gem_object_unlock(ctx->obj);
>   	if (err)
> @@ -115,7 +115,7 @@ static int gtt_get(struct context *ctx, unsigned long offset, u32 *v)
>   	u32 __iomem *map;
>   	int err = 0;
>   
> -	i915_gem_object_lock(ctx->obj);
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(ctx->obj, false);
>   	i915_gem_object_unlock(ctx->obj);
>   	if (err)
> @@ -147,7 +147,7 @@ static int wc_set(struct context *ctx, unsigned long offset, u32 v)
>   	u32 *map;
>   	int err;
>   
> -	i915_gem_object_lock(ctx->obj);
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_set_to_wc_domain(ctx->obj, true);
>   	i915_gem_object_unlock(ctx->obj);
>   	if (err)
> @@ -170,7 +170,7 @@ static int wc_get(struct context *ctx, unsigned long offset, u32 *v)
>   	u32 *map;
>   	int err;
>   
> -	i915_gem_object_lock(ctx->obj);
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_set_to_wc_domain(ctx->obj, false);
>   	i915_gem_object_unlock(ctx->obj);
>   	if (err)
> @@ -193,7 +193,7 @@ static int gpu_set(struct context *ctx, unsigned long offset, u32 v)
>   	u32 *cs;
>   	int err;
>   
> -	i915_gem_object_lock(ctx->obj);
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(ctx->obj, true);
>   	i915_gem_object_unlock(ctx->obj);
>   	if (err)
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> index b81978890641..438c15ef2184 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> @@ -950,7 +950,7 @@ emit_rpcs_query(struct drm_i915_gem_object *obj,
>   	if (IS_ERR(vma))
>   		return PTR_ERR(vma);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(obj, false);
>   	i915_gem_object_unlock(obj);
>   	if (err)
> @@ -1706,7 +1706,7 @@ static int read_from_scratch(struct i915_gem_context *ctx,
>   
>   	i915_request_add(rq);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_cpu_domain(obj, false);
>   	i915_gem_object_unlock(obj);
>   	if (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 9c7402ce5bf9..9fb95a45bcad 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_mman.c
> @@ -103,7 +103,7 @@ static int check_partial_mapping(struct drm_i915_gem_object *obj,
>   	GEM_BUG_ON(i915_gem_object_get_tiling(obj) != tile->tiling);
>   	GEM_BUG_ON(i915_gem_object_get_stride(obj) != tile->stride);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(obj, true);
>   	i915_gem_object_unlock(obj);
>   	if (err) {
> @@ -188,7 +188,7 @@ static int check_partial_mappings(struct drm_i915_gem_object *obj,
>   	GEM_BUG_ON(i915_gem_object_get_tiling(obj) != tile->tiling);
>   	GEM_BUG_ON(i915_gem_object_get_stride(obj) != tile->stride);
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(obj, true);
>   	i915_gem_object_unlock(obj);
>   	if (err) {
> diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_phys.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_phys.c
> index 34932871b3a5..a94243dc4c5c 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_phys.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_phys.c
> @@ -44,7 +44,7 @@ static int mock_phys_object(void *arg)
>   	}
>   
>   	/* Make the object dirty so that put_pages must do copy back the data */
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_gtt_domain(obj, true);
>   	i915_gem_object_unlock(obj);
>   	if (err) {
> diff --git a/drivers/gpu/drm/i915/gt/selftest_workarounds.c b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> index febc9e6692ba..61a0532d0f3d 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_workarounds.c
> @@ -214,7 +214,7 @@ static int check_whitelist(struct i915_gem_context *ctx,
>   		return PTR_ERR(results);
>   
>   	err = 0;
> -	i915_gem_object_lock(results);
> +	i915_gem_object_lock(results, NULL);
>   	intel_wedge_on_timeout(&wedge, engine->gt, HZ / 5) /* safety net! */
>   		err = i915_gem_object_set_to_cpu_domain(results, false);
>   	i915_gem_object_unlock(results);
> diff --git a/drivers/gpu/drm/i915/gvt/cmd_parser.c b/drivers/gpu/drm/i915/gvt/cmd_parser.c
> index f1940939260a..943c8d232703 100644
> --- a/drivers/gpu/drm/i915/gvt/cmd_parser.c
> +++ b/drivers/gpu/drm/i915/gvt/cmd_parser.c
> @@ -2982,7 +2982,7 @@ static int shadow_indirect_ctx(struct intel_shadow_wa_ctx *wa_ctx)
>   		goto put_obj;
>   	}
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	ret = i915_gem_object_set_to_cpu_domain(obj, false);
>   	i915_gem_object_unlock(obj);
>   	if (ret) {
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 9aa3066cb75d..1e06752835e5 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -420,7 +420,7 @@ i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
>   		GEM_BUG_ON(!drm_mm_node_allocated(&node));
>   	}
>   
> -	ret = i915_gem_object_lock_interruptible(obj);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		goto out_unpin;
>   
> @@ -619,7 +619,7 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj,
>   		GEM_BUG_ON(!drm_mm_node_allocated(&node));
>   	}
>   
> -	ret = i915_gem_object_lock_interruptible(obj);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		goto out_unpin;
>   
> @@ -1290,7 +1290,7 @@ int i915_gem_freeze_late(struct drm_i915_private *i915)
>   	i915_gem_drain_freed_objects(i915);
>   
>   	list_for_each_entry(obj, &i915->mm.shrink_list, mm.link) {
> -		i915_gem_object_lock(obj);
> +		i915_gem_object_lock(obj, NULL);
>   		drm_WARN_ON(&i915->drm,
>   			    i915_gem_object_set_to_cpu_domain(obj, true));
>   		i915_gem_object_unlock(obj);
> @@ -1344,6 +1344,52 @@ int i915_gem_open(struct drm_i915_private *i915, struct drm_file *file)
>   	return ret;
>   }
>   
> +void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ww, bool intr)
> +{
> +	ww_acquire_init(&ww->ctx, &reservation_ww_class);
> +	INIT_LIST_HEAD(&ww->obj_list);
> +	ww->intr = intr;
> +	ww->contended = NULL;
> +}
> +
> +static void i915_gem_ww_ctx_unlock_all(struct i915_gem_ww_ctx *ww)
> +{
> +	struct drm_i915_gem_object *obj;
> +
> +	while ((obj = list_first_entry_or_null(&ww->obj_list, struct drm_i915_gem_object, obj_link))) {

I wanted to ask whether you think this is faster than 
for_each_list_entry, but then also realized you can optimise further by 
not bothering to list_del (since you know the whole list is going away). 
If you are not allowing ww ctx reuse you don't even need to re-init the 
list_head at the end.

> +		list_del(&obj->obj_link);
> +		i915_gem_object_unlock(obj);
> +	}
> +}
> +
> +void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ww)
> +{
> +	i915_gem_ww_ctx_unlock_all(ww);
> +	WARN_ON(ww->contended);

Unless I am missing something this feels like a GEM_BUG_ON condition 
(translated: we should be confident after testing it is impossible to hit).

Or it is allowed to not try the backoff on -EDEADLK? Backoff is the only 
place which resets the ww->contended, right? In this case WARN_ON would 
be wrong, but you probably did not went for this design. Should it be 
supported?

> +	ww_acquire_fini(&ww->ctx);
> +}
> +
> +int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ww)
> +{
> +	int ret = 0;
> +
> +	if (WARN_ON(!ww->contended))
> +		return -EINVAL;
> +
> +	i915_gem_ww_ctx_unlock_all(ww);
> +	if (ww->intr)
> +		ret = dma_resv_lock_slow_interruptible(ww->contended->base.resv, &ww->ctx);
> +	else
> +		dma_resv_lock_slow(ww->contended->base.resv, &ww->ctx);
> +
> +	if (!ret)
> +		list_add_tail(&ww->contended->obj_link, &ww->obj_list);
> +
> +	ww->contended = NULL;
> +
> +	return ret;
> +}
> +
>   #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
>   #include "selftests/mock_gem_device.c"
>   #include "selftests/i915_gem.c"
> diff --git a/drivers/gpu/drm/i915/i915_gem.h b/drivers/gpu/drm/i915/i915_gem.h
> index 1753c84d6c0d..988755dbf4be 100644
> --- a/drivers/gpu/drm/i915/i915_gem.h
> +++ b/drivers/gpu/drm/i915/i915_gem.h
> @@ -116,4 +116,15 @@ static inline bool __tasklet_is_scheduled(struct tasklet_struct *t)
>   	return test_bit(TASKLET_STATE_SCHED, &t->state);
>   }
>   
> +struct i915_gem_ww_ctx {
> +	struct ww_acquire_ctx ctx;
> +	struct list_head obj_list;
> +	bool intr;
> +	struct drm_i915_gem_object *contended;
> +};
> +
> +void i915_gem_ww_ctx_init(struct i915_gem_ww_ctx *ctx, bool intr);
> +void i915_gem_ww_ctx_fini(struct i915_gem_ww_ctx *ctx);
> +int __must_check i915_gem_ww_ctx_backoff(struct i915_gem_ww_ctx *ctx);
> +
>   #endif /* __I915_GEM_H__ */
> diff --git a/drivers/gpu/drm/i915/selftests/i915_gem.c b/drivers/gpu/drm/i915/selftests/i915_gem.c
> index 88d400b9df88..23a6132c5f4e 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_gem.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_gem.c
> @@ -199,11 +199,52 @@ static int igt_gem_hibernate(void *arg)
>   	return err;
>   }
>   
> +static int igt_gem_ww_ctx(void *arg)
> +{
> +	struct drm_i915_private *i915 = arg;
> +	struct drm_i915_gem_object *obj, *obj2;
> +	struct i915_gem_ww_ctx ww;
> +	int err = 0;
> +
> +	obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
> +	if (IS_ERR(obj))
> +		return PTR_ERR(obj);
> +
> +	obj2 = i915_gem_object_create_internal(i915, PAGE_SIZE);
> +	if (IS_ERR(obj)) {

Wrong obj ^^^ vvv.

> +		err = PTR_ERR(obj);
> +		goto put1;
> +	}
> +
> +	i915_gem_ww_ctx_init(&ww, true);

Need to expand with non-interruptible, interruptible and mixed.

> +retry:
> +	/* Lock the objects, twice for good measure (-EALREADY handling) */
> +	err = i915_gem_object_lock(obj, &ww);
> +	if (!err)
> +		err = i915_gem_object_lock_interruptible(obj, &ww);

This is -EALREADY on the 1st pass.

> +	if (!err)
> +		err = i915_gem_object_lock_interruptible(obj2, &ww);
> +	if (!err)
> +		err = i915_gem_object_lock(obj2, &ww);

And this is -EALREADY again?

> +
> +	if (err == -EDEADLK) {

How do we get here with a single locking context?

> +		err = i915_gem_ww_ctx_backoff(&ww);
> +		if (!err)
> +			goto retry;
> +	}
> +	i915_gem_ww_ctx_fini(&ww);
> +	i915_gem_object_put(obj2);
> +put1:
> +	i915_gem_object_put(obj);
> +	return err;
> +}
> +
>   int i915_gem_live_selftests(struct drm_i915_private *i915)
>   {
>   	static const struct i915_subtest tests[] = {
>   		SUBTEST(igt_gem_suspend),
>   		SUBTEST(igt_gem_hibernate),
> +		SUBTEST(igt_gem_ww_ctx),
>   	};
>   
>   	if (intel_gt_is_wedged(&i915->gt))
> diff --git a/drivers/gpu/drm/i915/selftests/i915_vma.c b/drivers/gpu/drm/i915/selftests/i915_vma.c
> index af89c7fc8f59..88c5e9acb84c 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_vma.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_vma.c
> @@ -892,7 +892,7 @@ static int igt_vma_remapped_gtt(void *arg)
>   			unsigned int x, y;
>   			int err;
>   
> -			i915_gem_object_lock(obj);
> +			i915_gem_object_lock(obj, NULL);
>   			err = i915_gem_object_set_to_gtt_domain(obj, true);
>   			i915_gem_object_unlock(obj);
>   			if (err)
> diff --git a/drivers/gpu/drm/i915/selftests/intel_memory_region.c b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
> index 6e80d99048e4..957a7a52def7 100644
> --- a/drivers/gpu/drm/i915/selftests/intel_memory_region.c
> +++ b/drivers/gpu/drm/i915/selftests/intel_memory_region.c
> @@ -509,7 +509,7 @@ static int igt_lmem_write_cpu(void *arg)
>   	if (err)
>   		goto out_unpin;
>   
> -	i915_gem_object_lock(obj);
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_set_to_wc_domain(obj, true);
>   	i915_gem_object_unlock(obj);
>   	if (err)
> 

Regards,

Tvrtko


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