[PATCH 1/2] dma-buf: fix inconsistent debug print v2

[PATCH 1/2] dma-buf: fix inconsistent debug print v2

[Christian König]

Drop the whole rcu handling since we are holding the resv lock anyway.

v2: drop all rcu handling instead.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-buf.c | 27 +++++++++------------------
 1 file changed, 9 insertions(+), 18 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index eadd1eaa2fb5..ee04fb442015 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1349,15 +1349,14 @@ EXPORT_SYMBOL_GPL(dma_buf_vunmap);
 #ifdef CONFIG_DEBUG_FS
 static int dma_buf_debug_show(struct seq_file *s, void *unused)
 {
-	int ret;
 	struct dma_buf *buf_obj;
 	struct dma_buf_attachment *attach_obj;
 	struct dma_resv *robj;
 	struct dma_resv_list *fobj;
 	struct dma_fence *fence;
-	unsigned seq;
 	int count = 0, attach_count, shared_count, i;
 	size_t size = 0;
+	int ret;
 
 	ret = mutex_lock_interruptible(&db_list.lock);
 
@@ -1383,33 +1382,25 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
 				buf_obj->name ?: "");
 
 		robj = buf_obj->resv;
-		while (true) {
-			seq = read_seqcount_begin(&robj->seq);
-			rcu_read_lock();
-			fobj = rcu_dereference(robj->fence);
-			shared_count = fobj ? fobj->shared_count : 0;
-			fence = rcu_dereference(robj->fence_excl);
-			if (!read_seqcount_retry(&robj->seq, seq))
-				break;
-			rcu_read_unlock();
-		}
-
+		fence = rcu_dereference_protected(robj->fence_excl,
+						  dma_resv_held(robj));
 		if (fence)
 			seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
 				   fence->ops->get_driver_name(fence),
 				   fence->ops->get_timeline_name(fence),
 				   dma_fence_is_signaled(fence) ? "" : "un");
+
+		fobj = rcu_dereference_protected(robj->fence,
+						 dma_resv_held(robj));
+		shared_count = fobj ? fobj->shared_count : 0;
 		for (i = 0; i < shared_count; i++) {
-			fence = rcu_dereference(fobj->shared[i]);
-			if (!dma_fence_get_rcu(fence))
-				continue;
+			fence = rcu_dereference_protected(fobj->shared[i],
+							  dma_resv_held(robj));
 			seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
 				   fence->ops->get_driver_name(fence),
 				   fence->ops->get_timeline_name(fence),
 				   dma_fence_is_signaled(fence) ? "" : "un");
-			dma_fence_put(fence);
 		}
-		rcu_read_unlock();
 
 		seq_puts(s, "\tAttached Devices:\n");
 		attach_count = 0;
-- 
2.25.1

[PATCH 2/2] dma-buf: add SPDX header and fix style in dma-resv.c

[Christian König]

dma_resv_lockdep() seems to have some space/tab mixups. Fix that and
move the function to the end of the file.

Also fix some minor things checkpatch.pl pointed out while at it.

No functional change.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 128 +++++++++++++++++++------------------
 1 file changed, 65 insertions(+), 63 deletions(-)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 6ddbeb5dfbf6..87f5d82d992a 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: MIT
 /*
  * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
  *
@@ -92,49 +93,6 @@ static void dma_resv_list_free(struct dma_resv_list *list)
 	kfree_rcu(list, rcu);
 }
 
-#if IS_ENABLED(CONFIG_LOCKDEP)
-static int __init dma_resv_lockdep(void)
-{
-	struct mm_struct *mm = mm_alloc();
-	struct ww_acquire_ctx ctx;
-	struct dma_resv obj;
-	struct address_space mapping;
-	int ret;
-
-	if (!mm)
-		return -ENOMEM;
-
-	dma_resv_init(&obj);
-	address_space_init_once(&mapping);
-
-	mmap_read_lock(mm);
-	ww_acquire_init(&ctx, &reservation_ww_class);
-	ret = dma_resv_lock(&obj, &ctx);
-	if (ret == -EDEADLK)
-		dma_resv_lock_slow(&obj, &ctx);
-	fs_reclaim_acquire(GFP_KERNEL);
-	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
-	i_mmap_lock_write(&mapping);
-	i_mmap_unlock_write(&mapping);
-#ifdef CONFIG_MMU_NOTIFIER
-	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
-	__dma_fence_might_wait();
-	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
-#else
-	__dma_fence_might_wait();
-#endif
-	fs_reclaim_release(GFP_KERNEL);
-	ww_mutex_unlock(&obj.lock);
-	ww_acquire_fini(&ctx);
-	mmap_read_unlock(mm);
-	
-	mmput(mm);
-
-	return 0;
-}
-subsys_initcall(dma_resv_lockdep);
-#endif
-
 /**
  * dma_resv_init - initialize a reservation object
  * @obj: the reservation object
@@ -196,9 +154,7 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
 	if (old && old->shared_max) {
 		if ((old->shared_count + num_fences) <= old->shared_max)
 			return 0;
-		else
-			max = max(old->shared_count + num_fences,
-				  old->shared_max * 2);
+		max = max(old->shared_count + num_fences, old->shared_max * 2);
 	} else {
 		max = max(4ul, roundup_pow_of_two(num_fences));
 	}
@@ -337,17 +293,17 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
 EXPORT_SYMBOL(dma_resv_add_excl_fence);
 
 /**
-* dma_resv_copy_fences - Copy all fences from src to dst.
-* @dst: the destination reservation object
-* @src: the source reservation object
-*
-* Copy all fences from src to dst. dst-lock must be held.
-*/
+ * dma_resv_copy_fences - Copy all fences from src to dst.
+ * @dst: the destination reservation object
+ * @src: the source reservation object
+ *
+ * Copy all fences from src to dst. dst-lock must be held.
+ */
 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 {
 	struct dma_resv_list *src_list, *dst_list;
 	struct dma_fence *old, *new;
-	unsigned i;
+	unsigned int i;
 
 	dma_resv_assert_held(dst);
 
@@ -356,7 +312,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 
 retry:
 	if (src_list) {
-		unsigned shared_count = src_list->shared_count;
+		unsigned int shared_count = src_list->shared_count;
 
 		rcu_read_unlock();
 
@@ -373,6 +329,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 
 		dst_list->shared_count = 0;
 		for (i = 0; i < src_list->shared_count; ++i) {
+			struct dma_fence __rcu **dst;
 			struct dma_fence *fence;
 
 			fence = rcu_dereference(src_list->shared[i]);
@@ -391,7 +348,8 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
 				continue;
 			}
 
-			rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
+			dst = &dst_list->shared[dst_list->shared_count++];
+			rcu_assign_pointer(*dst, fence);
 		}
 	} else {
 		dst_list = NULL;
@@ -431,7 +389,7 @@ EXPORT_SYMBOL(dma_resv_copy_fences);
  */
 int dma_resv_get_fences_rcu(struct dma_resv *obj,
 			    struct dma_fence **pfence_excl,
-			    unsigned *pshared_count,
+			    unsigned int *pshared_count,
 			    struct dma_fence ***pshared)
 {
 	struct dma_fence **shared = NULL;
@@ -533,9 +491,9 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
 			       bool wait_all, bool intr,
 			       unsigned long timeout)
 {
-	struct dma_fence *fence;
-	unsigned seq, shared_count;
 	long ret = timeout ? timeout : 1;
+	unsigned int seq, shared_count;
+	struct dma_fence *fence;
 	int i;
 
 retry:
@@ -565,8 +523,9 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
 			shared_count = fobj->shared_count;
 
 		for (i = 0; !fence && i < shared_count; ++i) {
-			struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
+			struct dma_fence *lfence;
 
+			lfence = rcu_dereference(fobj->shared[i]);
 			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
 				     &lfence->flags))
 				continue;
@@ -633,7 +592,7 @@ static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
  */
 bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
 {
-	unsigned seq, shared_count;
+	unsigned int seq, shared_count;
 	int ret;
 
 	rcu_read_lock();
@@ -643,16 +602,16 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
 	seq = read_seqcount_begin(&obj->seq);
 
 	if (test_all) {
-		unsigned i;
-
 		struct dma_resv_list *fobj = rcu_dereference(obj->fence);
+		unsigned int i;
 
 		if (fobj)
 			shared_count = fobj->shared_count;
 
 		for (i = 0; i < shared_count; ++i) {
-			struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
+			struct dma_fence *fence;
 
+			fence = rcu_dereference(fobj->shared[i]);
 			ret = dma_resv_test_signaled_single(fence);
 			if (ret < 0)
 				goto retry;
@@ -681,3 +640,46 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
 	return ret;
 }
 EXPORT_SYMBOL_GPL(dma_resv_test_signaled_rcu);
+
+#if IS_ENABLED(CONFIG_LOCKDEP)
+static int __init dma_resv_lockdep(void)
+{
+	struct mm_struct *mm = mm_alloc();
+	struct ww_acquire_ctx ctx;
+	struct dma_resv obj;
+	struct address_space mapping;
+	int ret;
+
+	if (!mm)
+		return -ENOMEM;
+
+	dma_resv_init(&obj);
+	address_space_init_once(&mapping);
+
+	mmap_read_lock(mm);
+	ww_acquire_init(&ctx, &reservation_ww_class);
+	ret = dma_resv_lock(&obj, &ctx);
+	if (ret == -EDEADLK)
+		dma_resv_lock_slow(&obj, &ctx);
+	fs_reclaim_acquire(GFP_KERNEL);
+	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
+	i_mmap_lock_write(&mapping);
+	i_mmap_unlock_write(&mapping);
+#ifdef CONFIG_MMU_NOTIFIER
+	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
+	__dma_fence_might_wait();
+	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
+#else
+	__dma_fence_might_wait();
+#endif
+	fs_reclaim_release(GFP_KERNEL);
+	ww_mutex_unlock(&obj.lock);
+	ww_acquire_fini(&ctx);
+	mmap_read_unlock(mm);
+
+	mmput(mm);
+
+	return 0;
+}
+subsys_initcall(dma_resv_lockdep);
+#endif
-- 
2.25.1

Re: [PATCH 1/2] dma-buf: fix inconsistent debug print v2

[Daniel Vetter]

On Wed, Jun 02, 2021 at 04:03:58PM +0200, Christian König wrote:
> Drop the whole rcu handling since we are holding the resv lock anyway.
> 
> v2: drop all rcu handling instead.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/dma-buf/dma-buf.c | 27 +++++++++------------------
>  1 file changed, 9 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index eadd1eaa2fb5..ee04fb442015 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -1349,15 +1349,14 @@ EXPORT_SYMBOL_GPL(dma_buf_vunmap);
>  #ifdef CONFIG_DEBUG_FS
>  static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  {
> -	int ret;
>  	struct dma_buf *buf_obj;
>  	struct dma_buf_attachment *attach_obj;
>  	struct dma_resv *robj;
>  	struct dma_resv_list *fobj;
>  	struct dma_fence *fence;
> -	unsigned seq;
>  	int count = 0, attach_count, shared_count, i;
>  	size_t size = 0;
> +	int ret;
>  
>  	ret = mutex_lock_interruptible(&db_list.lock);
>  
> @@ -1383,33 +1382,25 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  				buf_obj->name ?: "");
>  
>  		robj = buf_obj->resv;
> -		while (true) {
> -			seq = read_seqcount_begin(&robj->seq);
> -			rcu_read_lock();
> -			fobj = rcu_dereference(robj->fence);
> -			shared_count = fobj ? fobj->shared_count : 0;
> -			fence = rcu_dereference(robj->fence_excl);
> -			if (!read_seqcount_retry(&robj->seq, seq))
> -				break;
> -			rcu_read_unlock();
> -		}
> -
> +		fence = rcu_dereference_protected(robj->fence_excl,
> +						  dma_resv_held(robj));
>  		if (fence)
>  			seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
>  				   fence->ops->get_driver_name(fence),
>  				   fence->ops->get_timeline_name(fence),
>  				   dma_fence_is_signaled(fence) ? "" : "un");
> +
> +		fobj = rcu_dereference_protected(robj->fence,
> +						 dma_resv_held(robj));
> +		shared_count = fobj ? fobj->shared_count : 0;
>  		for (i = 0; i < shared_count; i++) {
> -			fence = rcu_dereference(fobj->shared[i]);
> -			if (!dma_fence_get_rcu(fence))
> -				continue;
> +			fence = rcu_dereference_protected(fobj->shared[i],
> +							  dma_resv_held(robj));
>  			seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
>  				   fence->ops->get_driver_name(fence),
>  				   fence->ops->get_timeline_name(fence),
>  				   dma_fence_is_signaled(fence) ? "" : "un");
> -			dma_fence_put(fence);
>  		}
> -		rcu_read_unlock();
>  
>  		seq_puts(s, "\tAttached Devices:\n");
>  		attach_count = 0;
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH 2/2] dma-buf: add SPDX header and fix style in dma-resv.c

[Daniel Vetter]

On Wed, Jun 02, 2021 at 04:03:59PM +0200, Christian König wrote:
> dma_resv_lockdep() seems to have some space/tab mixups. Fix that and
> move the function to the end of the file.
> 
> Also fix some minor things checkpatch.pl pointed out while at it.
> 
> No functional change.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> ---
>  drivers/dma-buf/dma-resv.c | 128 +++++++++++++++++++------------------
>  1 file changed, 65 insertions(+), 63 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index 6ddbeb5dfbf6..87f5d82d992a 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -1,3 +1,4 @@
> +// SPDX-License-Identifier: MIT
>  /*
>   * Copyright (C) 2012-2014 Canonical Ltd (Maarten Lankhorst)
>   *
> @@ -92,49 +93,6 @@ static void dma_resv_list_free(struct dma_resv_list *list)
>  	kfree_rcu(list, rcu);
>  }
>  
> -#if IS_ENABLED(CONFIG_LOCKDEP)
> -static int __init dma_resv_lockdep(void)
> -{
> -	struct mm_struct *mm = mm_alloc();
> -	struct ww_acquire_ctx ctx;
> -	struct dma_resv obj;
> -	struct address_space mapping;
> -	int ret;
> -
> -	if (!mm)
> -		return -ENOMEM;
> -
> -	dma_resv_init(&obj);
> -	address_space_init_once(&mapping);
> -
> -	mmap_read_lock(mm);
> -	ww_acquire_init(&ctx, &reservation_ww_class);
> -	ret = dma_resv_lock(&obj, &ctx);
> -	if (ret == -EDEADLK)
> -		dma_resv_lock_slow(&obj, &ctx);
> -	fs_reclaim_acquire(GFP_KERNEL);
> -	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
> -	i_mmap_lock_write(&mapping);
> -	i_mmap_unlock_write(&mapping);
> -#ifdef CONFIG_MMU_NOTIFIER
> -	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
> -	__dma_fence_might_wait();
> -	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
> -#else
> -	__dma_fence_might_wait();
> -#endif
> -	fs_reclaim_release(GFP_KERNEL);
> -	ww_mutex_unlock(&obj.lock);
> -	ww_acquire_fini(&ctx);
> -	mmap_read_unlock(mm);
> -	
> -	mmput(mm);
> -
> -	return 0;
> -}
> -subsys_initcall(dma_resv_lockdep);
> -#endif
> -
>  /**
>   * dma_resv_init - initialize a reservation object
>   * @obj: the reservation object
> @@ -196,9 +154,7 @@ int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences)
>  	if (old && old->shared_max) {
>  		if ((old->shared_count + num_fences) <= old->shared_max)
>  			return 0;
> -		else
> -			max = max(old->shared_count + num_fences,
> -				  old->shared_max * 2);
> +		max = max(old->shared_count + num_fences, old->shared_max * 2);
>  	} else {
>  		max = max(4ul, roundup_pow_of_two(num_fences));
>  	}
> @@ -337,17 +293,17 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
>  EXPORT_SYMBOL(dma_resv_add_excl_fence);
>  
>  /**
> -* dma_resv_copy_fences - Copy all fences from src to dst.
> -* @dst: the destination reservation object
> -* @src: the source reservation object
> -*
> -* Copy all fences from src to dst. dst-lock must be held.
> -*/
> + * dma_resv_copy_fences - Copy all fences from src to dst.
> + * @dst: the destination reservation object
> + * @src: the source reservation object
> + *
> + * Copy all fences from src to dst. dst-lock must be held.
> + */
>  int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
>  {
>  	struct dma_resv_list *src_list, *dst_list;
>  	struct dma_fence *old, *new;
> -	unsigned i;
> +	unsigned int i;
>  
>  	dma_resv_assert_held(dst);
>  
> @@ -356,7 +312,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
>  
>  retry:
>  	if (src_list) {
> -		unsigned shared_count = src_list->shared_count;
> +		unsigned int shared_count = src_list->shared_count;
>  
>  		rcu_read_unlock();
>  
> @@ -373,6 +329,7 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
>  
>  		dst_list->shared_count = 0;
>  		for (i = 0; i < src_list->shared_count; ++i) {
> +			struct dma_fence __rcu **dst;
>  			struct dma_fence *fence;
>  
>  			fence = rcu_dereference(src_list->shared[i]);
> @@ -391,7 +348,8 @@ int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src)
>  				continue;
>  			}
>  
> -			rcu_assign_pointer(dst_list->shared[dst_list->shared_count++], fence);
> +			dst = &dst_list->shared[dst_list->shared_count++];
> +			rcu_assign_pointer(*dst, fence);
>  		}
>  	} else {
>  		dst_list = NULL;
> @@ -431,7 +389,7 @@ EXPORT_SYMBOL(dma_resv_copy_fences);
>   */
>  int dma_resv_get_fences_rcu(struct dma_resv *obj,
>  			    struct dma_fence **pfence_excl,
> -			    unsigned *pshared_count,
> +			    unsigned int *pshared_count,
>  			    struct dma_fence ***pshared)
>  {
>  	struct dma_fence **shared = NULL;
> @@ -533,9 +491,9 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
>  			       bool wait_all, bool intr,
>  			       unsigned long timeout)
>  {
> -	struct dma_fence *fence;
> -	unsigned seq, shared_count;
>  	long ret = timeout ? timeout : 1;
> +	unsigned int seq, shared_count;
> +	struct dma_fence *fence;
>  	int i;
>  
>  retry:
> @@ -565,8 +523,9 @@ long dma_resv_wait_timeout_rcu(struct dma_resv *obj,
>  			shared_count = fobj->shared_count;
>  
>  		for (i = 0; !fence && i < shared_count; ++i) {
> -			struct dma_fence *lfence = rcu_dereference(fobj->shared[i]);
> +			struct dma_fence *lfence;
>  
> +			lfence = rcu_dereference(fobj->shared[i]);
>  			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
>  				     &lfence->flags))
>  				continue;
> @@ -633,7 +592,7 @@ static inline int dma_resv_test_signaled_single(struct dma_fence *passed_fence)
>   */
>  bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
>  {
> -	unsigned seq, shared_count;
> +	unsigned int seq, shared_count;
>  	int ret;
>  
>  	rcu_read_lock();
> @@ -643,16 +602,16 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
>  	seq = read_seqcount_begin(&obj->seq);
>  
>  	if (test_all) {
> -		unsigned i;
> -
>  		struct dma_resv_list *fobj = rcu_dereference(obj->fence);
> +		unsigned int i;
>  
>  		if (fobj)
>  			shared_count = fobj->shared_count;
>  
>  		for (i = 0; i < shared_count; ++i) {
> -			struct dma_fence *fence = rcu_dereference(fobj->shared[i]);
> +			struct dma_fence *fence;
>  
> +			fence = rcu_dereference(fobj->shared[i]);
>  			ret = dma_resv_test_signaled_single(fence);
>  			if (ret < 0)
>  				goto retry;
> @@ -681,3 +640,46 @@ bool dma_resv_test_signaled_rcu(struct dma_resv *obj, bool test_all)
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(dma_resv_test_signaled_rcu);
> +
> +#if IS_ENABLED(CONFIG_LOCKDEP)
> +static int __init dma_resv_lockdep(void)
> +{
> +	struct mm_struct *mm = mm_alloc();
> +	struct ww_acquire_ctx ctx;
> +	struct dma_resv obj;
> +	struct address_space mapping;
> +	int ret;
> +
> +	if (!mm)
> +		return -ENOMEM;
> +
> +	dma_resv_init(&obj);
> +	address_space_init_once(&mapping);
> +
> +	mmap_read_lock(mm);
> +	ww_acquire_init(&ctx, &reservation_ww_class);
> +	ret = dma_resv_lock(&obj, &ctx);
> +	if (ret == -EDEADLK)
> +		dma_resv_lock_slow(&obj, &ctx);
> +	fs_reclaim_acquire(GFP_KERNEL);
> +	/* for unmap_mapping_range on trylocked buffer objects in shrinkers */
> +	i_mmap_lock_write(&mapping);
> +	i_mmap_unlock_write(&mapping);
> +#ifdef CONFIG_MMU_NOTIFIER
> +	lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);
> +	__dma_fence_might_wait();
> +	lock_map_release(&__mmu_notifier_invalidate_range_start_map);
> +#else
> +	__dma_fence_might_wait();
> +#endif
> +	fs_reclaim_release(GFP_KERNEL);
> +	ww_mutex_unlock(&obj.lock);
> +	ww_acquire_fini(&ctx);
> +	mmap_read_unlock(mm);
> +
> +	mmput(mm);
> +
> +	return 0;
> +}
> +subsys_initcall(dma_resv_lockdep);
> +#endif
> -- 
> 2.25.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch