Re: [PATCH 05/23] drm/i915: Remove locking from i915_gem_object_prepare_read/write

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 03/07/2020 13:22, Maarten Lankhorst wrote:
> Execbuffer submission will perform its own WW locking, and we
> cannot rely on the implicit lock there.
>
> This also makes it clear that the GVT code will get a lockdep splat when
> multiple batchbuffer shadows need to be performed in the same instance,
> fix that up.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>

You have my r-b for this one from the previous round.

Regards,

Tvrtko

> ---
>   drivers/gpu/drm/i915/gem/i915_gem_domain.c    | 20 ++++++-------------
>   .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 13 ++++++++++--
>   drivers/gpu/drm/i915/gem/i915_gem_object.h    |  1 -
>   .../gpu/drm/i915/gem/selftests/huge_pages.c   |  5 ++++-
>   .../i915/gem/selftests/i915_gem_coherency.c   | 14 +++++++++----
>   .../drm/i915/gem/selftests/i915_gem_context.c | 12 ++++++++---
>   drivers/gpu/drm/i915/gvt/cmd_parser.c         |  1 +
>   drivers/gpu/drm/i915/i915_gem.c               | 20 +++++++++++++++++--
>   8 files changed, 59 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_domain.c b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> index c0acfc97fae3..8ebceebd11b0 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_domain.c
> @@ -576,19 +576,17 @@ 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, NULL);
> -	if (ret)
> -		return ret;
> +	assert_object_held(obj);
>   
>   	ret = i915_gem_object_wait(obj,
>   				   I915_WAIT_INTERRUPTIBLE,
>   				   MAX_SCHEDULE_TIMEOUT);
>   	if (ret)
> -		goto err_unlock;
> +		return ret;
>   
>   	ret = i915_gem_object_pin_pages(obj);
>   	if (ret)
> -		goto err_unlock;
> +		return ret;
>   
>   	if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_READ ||
>   	    !static_cpu_has(X86_FEATURE_CLFLUSH)) {
> @@ -616,8 +614,6 @@ int i915_gem_object_prepare_read(struct drm_i915_gem_object *obj,
>   
>   err_unpin:
>   	i915_gem_object_unpin_pages(obj);
> -err_unlock:
> -	i915_gem_object_unlock(obj);
>   	return ret;
>   }
>   
> @@ -630,20 +626,18 @@ 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, NULL);
> -	if (ret)
> -		return ret;
> +	assert_object_held(obj);
>   
>   	ret = i915_gem_object_wait(obj,
>   				   I915_WAIT_INTERRUPTIBLE |
>   				   I915_WAIT_ALL,
>   				   MAX_SCHEDULE_TIMEOUT);
>   	if (ret)
> -		goto err_unlock;
> +		return ret;
>   
>   	ret = i915_gem_object_pin_pages(obj);
>   	if (ret)
> -		goto err_unlock;
> +		return ret;
>   
>   	if (obj->cache_coherent & I915_BO_CACHE_COHERENT_FOR_WRITE ||
>   	    !static_cpu_has(X86_FEATURE_CLFLUSH)) {
> @@ -680,7 +674,5 @@ int i915_gem_object_prepare_write(struct drm_i915_gem_object *obj,
>   
>   err_unpin:
>   	i915_gem_object_unpin_pages(obj);
> -err_unlock:
> -	i915_gem_object_unlock(obj);
>   	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 370c1cbc4d3b..c2a4e499233b 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -996,11 +996,14 @@ static void reloc_cache_reset(struct reloc_cache *cache)
>   
>   	vaddr = unmask_page(cache->vaddr);
>   	if (cache->vaddr & KMAP) {
> +		struct drm_i915_gem_object *obj =
> +			(struct drm_i915_gem_object *)cache->node.mm;
>   		if (cache->vaddr & CLFLUSH_AFTER)
>   			mb();
>   
>   		kunmap_atomic(vaddr);
> -		i915_gem_object_finish_access((struct drm_i915_gem_object *)cache->node.mm);
> +		i915_gem_object_finish_access(obj);
> +		i915_gem_object_unlock(obj);
>   	} else {
>   		struct i915_ggtt *ggtt = cache_to_ggtt(cache);
>   
> @@ -1035,10 +1038,16 @@ static void *reloc_kmap(struct drm_i915_gem_object *obj,
>   		unsigned int flushes;
>   		int err;
>   
> -		err = i915_gem_object_prepare_write(obj, &flushes);
> +		err = i915_gem_object_lock_interruptible(obj, NULL);
>   		if (err)
>   			return ERR_PTR(err);
>   
> +		err = i915_gem_object_prepare_write(obj, &flushes);
> +		if (err) {
> +			i915_gem_object_unlock(obj);
> +			return ERR_PTR(err);
> +		}
> +
>   		BUILD_BUG_ON(KMAP & CLFLUSH_FLAGS);
>   		BUILD_BUG_ON((KMAP | CLFLUSH_FLAGS) & PAGE_MASK);
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index 5103067269b0..11b8e2735071 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -434,7 +434,6 @@ static inline void
>   i915_gem_object_finish_access(struct drm_i915_gem_object *obj)
>   {
>   	i915_gem_object_unpin_pages(obj);
> -	i915_gem_object_unlock(obj);
>   }
>   
>   static inline struct intel_engine_cs *
> diff --git a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> index eb2011ccb92b..fff11327a8da 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/huge_pages.c
> @@ -964,9 +964,10 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, u32 dword, u32 val)
>   	unsigned long n;
>   	int err;
>   
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_prepare_read(obj, &needs_flush);
>   	if (err)
> -		return err;
> +		goto err_unlock;
>   
>   	for (n = 0; n < obj->base.size >> PAGE_SHIFT; ++n) {
>   		u32 *ptr = kmap_atomic(i915_gem_object_get_page(obj, n));
> @@ -986,6 +987,8 @@ __cpu_check_shmem(struct drm_i915_gem_object *obj, u32 dword, u32 val)
>   	}
>   
>   	i915_gem_object_finish_access(obj);
> +err_unlock:
> +	i915_gem_object_unlock(obj);
>   
>   	return 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 1de2959b153c..dcdfc396f2f8 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_coherency.c
> @@ -27,9 +27,10 @@ static int cpu_set(struct context *ctx, unsigned long offset, u32 v)
>   	u32 *cpu;
>   	int err;
>   
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_prepare_write(ctx->obj, &needs_clflush);
>   	if (err)
> -		return err;
> +		goto out;
>   
>   	page = i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT);
>   	map = kmap_atomic(page);
> @@ -46,7 +47,9 @@ static int cpu_set(struct context *ctx, unsigned long offset, u32 v)
>   	kunmap_atomic(map);
>   	i915_gem_object_finish_access(ctx->obj);
>   
> -	return 0;
> +out:
> +	i915_gem_object_unlock(ctx->obj);
> +	return err;
>   }
>   
>   static int cpu_get(struct context *ctx, unsigned long offset, u32 *v)
> @@ -57,9 +60,10 @@ static int cpu_get(struct context *ctx, unsigned long offset, u32 *v)
>   	u32 *cpu;
>   	int err;
>   
> +	i915_gem_object_lock(ctx->obj, NULL);
>   	err = i915_gem_object_prepare_read(ctx->obj, &needs_clflush);
>   	if (err)
> -		return err;
> +		goto out;
>   
>   	page = i915_gem_object_get_page(ctx->obj, offset >> PAGE_SHIFT);
>   	map = kmap_atomic(page);
> @@ -73,7 +77,9 @@ static int cpu_get(struct context *ctx, unsigned long offset, u32 *v)
>   	kunmap_atomic(map);
>   	i915_gem_object_finish_access(ctx->obj);
>   
> -	return 0;
> +out:
> +	i915_gem_object_unlock(ctx->obj);
> +	return err;
>   }
>   
>   static int gtt_set(struct context *ctx, unsigned long offset, u32 v)
> 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 438c15ef2184..76671f587b9d 100644
> --- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> +++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_context.c
> @@ -461,9 +461,10 @@ static int cpu_fill(struct drm_i915_gem_object *obj, u32 value)
>   	unsigned int n, m, need_flush;
>   	int err;
>   
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_prepare_write(obj, &need_flush);
>   	if (err)
> -		return err;
> +		goto out;
>   
>   	for (n = 0; n < real_page_count(obj); n++) {
>   		u32 *map;
> @@ -479,7 +480,9 @@ static int cpu_fill(struct drm_i915_gem_object *obj, u32 value)
>   	i915_gem_object_finish_access(obj);
>   	obj->read_domains = I915_GEM_DOMAIN_GTT | I915_GEM_DOMAIN_CPU;
>   	obj->write_domain = 0;
> -	return 0;
> +out:
> +	i915_gem_object_unlock(obj);
> +	return err;
>   }
>   
>   static noinline int cpu_check(struct drm_i915_gem_object *obj,
> @@ -488,9 +491,10 @@ static noinline int cpu_check(struct drm_i915_gem_object *obj,
>   	unsigned int n, m, needs_flush;
>   	int err;
>   
> +	i915_gem_object_lock(obj, NULL);
>   	err = i915_gem_object_prepare_read(obj, &needs_flush);
>   	if (err)
> -		return err;
> +		goto out_unlock;
>   
>   	for (n = 0; n < real_page_count(obj); n++) {
>   		u32 *map;
> @@ -527,6 +531,8 @@ static noinline int cpu_check(struct drm_i915_gem_object *obj,
>   	}
>   
>   	i915_gem_object_finish_access(obj);
> +out_unlock:
> +	i915_gem_object_unlock(obj);
>   	return err;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/gvt/cmd_parser.c b/drivers/gpu/drm/i915/gvt/cmd_parser.c
> index 943c8d232703..d0a599b51bfe 100644
> --- a/drivers/gpu/drm/i915/gvt/cmd_parser.c
> +++ b/drivers/gpu/drm/i915/gvt/cmd_parser.c
> @@ -1923,6 +1923,7 @@ static int perform_bb_shadow(struct parser_exec_state *s)
>   	if (ret)
>   		goto err_unmap;
>   
> +	i915_gem_object_unlock(bb->obj);
>   	INIT_LIST_HEAD(&bb->list);
>   	list_add(&bb->list, &s->workload->shadow_bb);
>   
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 1e06752835e5..33f6f88c8b08 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -335,12 +335,20 @@ i915_gem_shmem_pread(struct drm_i915_gem_object *obj,
>   	u64 remain;
>   	int ret;
>   
> -	ret = i915_gem_object_prepare_read(obj, &needs_clflush);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		return ret;
>   
> +	ret = i915_gem_object_prepare_read(obj, &needs_clflush);
> +	if (ret) {
> +		i915_gem_object_unlock(obj);
> +		return ret;
> +	}
> +
>   	fence = i915_gem_object_lock_fence(obj);
>   	i915_gem_object_finish_access(obj);
> +	i915_gem_object_unlock(obj);
> +
>   	if (!fence)
>   		return -ENOMEM;
>   
> @@ -734,12 +742,20 @@ i915_gem_shmem_pwrite(struct drm_i915_gem_object *obj,
>   	u64 remain;
>   	int ret;
>   
> -	ret = i915_gem_object_prepare_write(obj, &needs_clflush);
> +	ret = i915_gem_object_lock_interruptible(obj, NULL);
>   	if (ret)
>   		return ret;
>   
> +	ret = i915_gem_object_prepare_write(obj, &needs_clflush);
> +	if (ret) {
> +		i915_gem_object_unlock(obj);
> +		return ret;
> +	}
> +
>   	fence = i915_gem_object_lock_fence(obj);
>   	i915_gem_object_finish_access(obj);
> +	i915_gem_object_unlock(obj);
> +
>   	if (!fence)
>   		return -ENOMEM;
>   
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