diff mbox series

[03/26] dma-buf: use new iterator in dma_resv_copy_fences

Message ID 20210917123513.1106-4-christian.koenig@amd.com (mailing list archive)
State New, archived
Headers show
Series [01/26] dma-buf: add dma_resv_for_each_fence_unlocked v2 | expand

Commit Message

Christian König Sept. 17, 2021, 12:34 p.m. UTC 
This makes the function much simpler since the complex
retry logic is now handled else where.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 86 ++++++++++++++++----------------------
 1 file changed, 35 insertions(+), 51 deletions(-)

Comments

Daniel Vetter Sept. 17, 2021, 2:35 p.m. UTC | #1 
On Fri, Sep 17, 2021 at 02:34:50PM +0200, Christian König wrote:
> This makes the function much simpler since the complex
> retry logic is now handled else where.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>  drivers/dma-buf/dma-resv.c | 86 ++++++++++++++++----------------------
>  1 file changed, 35 insertions(+), 51 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
> index a3c79a99fb44..406150dea5e4 100644
> --- a/drivers/dma-buf/dma-resv.c
> +++ b/drivers/dma-buf/dma-resv.c
> @@ -426,74 +426,58 @@ EXPORT_SYMBOL_GPL(dma_resv_iter_walk);
>   */
>  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 int i;
> +	struct dma_resv_iter cursor;
> +	struct dma_resv_list *list;
> +	struct dma_fence *f, *excl;
>  
>  	dma_resv_assert_held(dst);
>  
> -	rcu_read_lock();
> -	src_list = dma_resv_shared_list(src);
> -
> -retry:
> -	if (src_list) {
> -		unsigned int shared_count = src_list->shared_count;
> -
> -		rcu_read_unlock();
> +	list = NULL;
> +	excl = NULL;
>  
> -		dst_list = dma_resv_list_alloc(shared_count);
> -		if (!dst_list)
> -			return -ENOMEM;
> +	rcu_read_lock();
> +	dma_resv_iter_begin(&cursor, src, true);
> +	dma_resv_for_each_fence_unlocked(&cursor, f) {
>  
> -		rcu_read_lock();
> -		src_list = dma_resv_shared_list(src);
> -		if (!src_list || src_list->shared_count > shared_count) {
> -			kfree(dst_list);
> -			goto retry;
> -		}
> +		if (cursor.is_first) {

Maybe have a wrapper for this, like dma_resv_iter_is_reset or is_first or
is_restart (my preference) with some nice docs that this returns true
everytime we had to restart the sequence?

Otherwise I fully agree, this is so much better with all the hairy
restarting and get_rcu and test_bit shovelled away somewhere.

Either way (but I much prefer a wrapper for is_first):

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

> +			dma_resv_list_free(list);
> +			dma_fence_put(excl);
>  
> -		dst_list->shared_count = 0;
> -		for (i = 0; i < src_list->shared_count; ++i) {
> -			struct dma_fence __rcu **dst;
> -			struct dma_fence *fence;
> +			if (cursor.fences) {
> +				unsigned int cnt = cursor.fences->shared_count;
>  
> -			fence = rcu_dereference(src_list->shared[i]);
> -			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
> -				     &fence->flags))
> -				continue;
> +				rcu_read_unlock();
> +				list = dma_resv_list_alloc(cnt);
> +				if (!list) {
> +					dma_resv_iter_end(&cursor);
> +					return -ENOMEM;
> +				}
>  
> -			if (!dma_fence_get_rcu(fence)) {
> -				dma_resv_list_free(dst_list);
> -				src_list = dma_resv_shared_list(src);
> -				goto retry;
> -			}
> +				list->shared_count = 0;
> +				rcu_read_lock();
>  
> -			if (dma_fence_is_signaled(fence)) {
> -				dma_fence_put(fence);
> -				continue;
> +			} else {
> +				list = NULL;
>  			}
> -
> -			dst = &dst_list->shared[dst_list->shared_count++];
> -			rcu_assign_pointer(*dst, fence);
> +			excl = NULL;
>  		}
> -	} else {
> -		dst_list = NULL;
> -	}
>  
> -	new = dma_fence_get_rcu_safe(&src->fence_excl);
> +		dma_fence_get(f);
> +		if (dma_resv_iter_is_exclusive(&cursor))
> +			excl = f;
> +		else
> +			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
> +	}
> +	dma_resv_iter_end(&cursor);
>  	rcu_read_unlock();
>  
> -	src_list = dma_resv_shared_list(dst);
> -	old = dma_resv_excl_fence(dst);
> -
>  	write_seqcount_begin(&dst->seq);
> -	/* write_seqcount_begin provides the necessary memory barrier */
> -	RCU_INIT_POINTER(dst->fence_excl, new);
> -	RCU_INIT_POINTER(dst->fence, dst_list);
> +	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
> +	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
>  	write_seqcount_end(&dst->seq);
>  
> -	dma_resv_list_free(src_list);
> -	dma_fence_put(old);
> +	dma_resv_list_free(list);
> +	dma_fence_put(excl);
>  
>  	return 0;
>  }
> -- 
> 2.25.1
>
Christian König Sept. 20, 2021, 7:23 a.m. UTC | #2 
Am 17.09.21 um 16:35 schrieb Daniel Vetter:
> On Fri, Sep 17, 2021 at 02:34:50PM +0200, Christian König wrote:
>> This makes the function much simpler since the complex
>> retry logic is now handled else where.
>>
>> Signed-off-by: Christian König <christian.koenig@amd.com>
>> ---
>>   drivers/dma-buf/dma-resv.c | 86 ++++++++++++++++----------------------
>>   1 file changed, 35 insertions(+), 51 deletions(-)
>>
>> diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
>> index a3c79a99fb44..406150dea5e4 100644
>> --- a/drivers/dma-buf/dma-resv.c
>> +++ b/drivers/dma-buf/dma-resv.c
>> @@ -426,74 +426,58 @@ EXPORT_SYMBOL_GPL(dma_resv_iter_walk);
>>    */
>>   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 int i;
>> +	struct dma_resv_iter cursor;
>> +	struct dma_resv_list *list;
>> +	struct dma_fence *f, *excl;
>>   
>>   	dma_resv_assert_held(dst);
>>   
>> -	rcu_read_lock();
>> -	src_list = dma_resv_shared_list(src);
>> -
>> -retry:
>> -	if (src_list) {
>> -		unsigned int shared_count = src_list->shared_count;
>> -
>> -		rcu_read_unlock();
>> +	list = NULL;
>> +	excl = NULL;
>>   
>> -		dst_list = dma_resv_list_alloc(shared_count);
>> -		if (!dst_list)
>> -			return -ENOMEM;
>> +	rcu_read_lock();
>> +	dma_resv_iter_begin(&cursor, src, true);
>> +	dma_resv_for_each_fence_unlocked(&cursor, f) {
>>   
>> -		rcu_read_lock();
>> -		src_list = dma_resv_shared_list(src);
>> -		if (!src_list || src_list->shared_count > shared_count) {
>> -			kfree(dst_list);
>> -			goto retry;
>> -		}
>> +		if (cursor.is_first) {
> Maybe have a wrapper for this, like dma_resv_iter_is_reset or is_first or
> is_restart (my preference) with some nice docs that this returns true
> everytime we had to restart the sequence?

Exactly that's what I wanted to avoid since the is_first (or whatever) 
function should only be used inside of the dma_resv.c code.

On the other hand I can just make that static here and document that it 
should never be exported.

Christian.

>
> Otherwise I fully agree, this is so much better with all the hairy
> restarting and get_rcu and test_bit shovelled away somewhere.
>
> Either way (but I much prefer a wrapper for is_first):
>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>
>> +			dma_resv_list_free(list);
>> +			dma_fence_put(excl);
>>   
>> -		dst_list->shared_count = 0;
>> -		for (i = 0; i < src_list->shared_count; ++i) {
>> -			struct dma_fence __rcu **dst;
>> -			struct dma_fence *fence;
>> +			if (cursor.fences) {
>> +				unsigned int cnt = cursor.fences->shared_count;
>>   
>> -			fence = rcu_dereference(src_list->shared[i]);
>> -			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
>> -				     &fence->flags))
>> -				continue;
>> +				rcu_read_unlock();
>> +				list = dma_resv_list_alloc(cnt);
>> +				if (!list) {
>> +					dma_resv_iter_end(&cursor);
>> +					return -ENOMEM;
>> +				}
>>   
>> -			if (!dma_fence_get_rcu(fence)) {
>> -				dma_resv_list_free(dst_list);
>> -				src_list = dma_resv_shared_list(src);
>> -				goto retry;
>> -			}
>> +				list->shared_count = 0;
>> +				rcu_read_lock();
>>   
>> -			if (dma_fence_is_signaled(fence)) {
>> -				dma_fence_put(fence);
>> -				continue;
>> +			} else {
>> +				list = NULL;
>>   			}
>> -
>> -			dst = &dst_list->shared[dst_list->shared_count++];
>> -			rcu_assign_pointer(*dst, fence);
>> +			excl = NULL;
>>   		}
>> -	} else {
>> -		dst_list = NULL;
>> -	}
>>   
>> -	new = dma_fence_get_rcu_safe(&src->fence_excl);
>> +		dma_fence_get(f);
>> +		if (dma_resv_iter_is_exclusive(&cursor))
>> +			excl = f;
>> +		else
>> +			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
>> +	}
>> +	dma_resv_iter_end(&cursor);
>>   	rcu_read_unlock();
>>   
>> -	src_list = dma_resv_shared_list(dst);
>> -	old = dma_resv_excl_fence(dst);
>> -
>>   	write_seqcount_begin(&dst->seq);
>> -	/* write_seqcount_begin provides the necessary memory barrier */
>> -	RCU_INIT_POINTER(dst->fence_excl, new);
>> -	RCU_INIT_POINTER(dst->fence, dst_list);
>> +	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
>> +	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
>>   	write_seqcount_end(&dst->seq);
>>   
>> -	dma_resv_list_free(src_list);
>> -	dma_fence_put(old);
>> +	dma_resv_list_free(list);
>> +	dma_fence_put(excl);
>>   
>>   	return 0;
>>   }
>> -- 
>> 2.25.1
>>
diff mbox series

Patch

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index a3c79a99fb44..406150dea5e4 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -426,74 +426,58 @@  EXPORT_SYMBOL_GPL(dma_resv_iter_walk);
  */
 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 int i;
+	struct dma_resv_iter cursor;
+	struct dma_resv_list *list;
+	struct dma_fence *f, *excl;
 
 	dma_resv_assert_held(dst);
 
-	rcu_read_lock();
-	src_list = dma_resv_shared_list(src);
-
-retry:
-	if (src_list) {
-		unsigned int shared_count = src_list->shared_count;
-
-		rcu_read_unlock();
+	list = NULL;
+	excl = NULL;
 
-		dst_list = dma_resv_list_alloc(shared_count);
-		if (!dst_list)
-			return -ENOMEM;
+	rcu_read_lock();
+	dma_resv_iter_begin(&cursor, src, true);
+	dma_resv_for_each_fence_unlocked(&cursor, f) {
 
-		rcu_read_lock();
-		src_list = dma_resv_shared_list(src);
-		if (!src_list || src_list->shared_count > shared_count) {
-			kfree(dst_list);
-			goto retry;
-		}
+		if (cursor.is_first) {
+			dma_resv_list_free(list);
+			dma_fence_put(excl);
 
-		dst_list->shared_count = 0;
-		for (i = 0; i < src_list->shared_count; ++i) {
-			struct dma_fence __rcu **dst;
-			struct dma_fence *fence;
+			if (cursor.fences) {
+				unsigned int cnt = cursor.fences->shared_count;
 
-			fence = rcu_dereference(src_list->shared[i]);
-			if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
-				     &fence->flags))
-				continue;
+				rcu_read_unlock();
+				list = dma_resv_list_alloc(cnt);
+				if (!list) {
+					dma_resv_iter_end(&cursor);
+					return -ENOMEM;
+				}
 
-			if (!dma_fence_get_rcu(fence)) {
-				dma_resv_list_free(dst_list);
-				src_list = dma_resv_shared_list(src);
-				goto retry;
-			}
+				list->shared_count = 0;
+				rcu_read_lock();
 
-			if (dma_fence_is_signaled(fence)) {
-				dma_fence_put(fence);
-				continue;
+			} else {
+				list = NULL;
 			}
-
-			dst = &dst_list->shared[dst_list->shared_count++];
-			rcu_assign_pointer(*dst, fence);
+			excl = NULL;
 		}
-	} else {
-		dst_list = NULL;
-	}
 
-	new = dma_fence_get_rcu_safe(&src->fence_excl);
+		dma_fence_get(f);
+		if (dma_resv_iter_is_exclusive(&cursor))
+			excl = f;
+		else
+			RCU_INIT_POINTER(list->shared[list->shared_count++], f);
+	}
+	dma_resv_iter_end(&cursor);
 	rcu_read_unlock();
 
-	src_list = dma_resv_shared_list(dst);
-	old = dma_resv_excl_fence(dst);
-
 	write_seqcount_begin(&dst->seq);
-	/* write_seqcount_begin provides the necessary memory barrier */
-	RCU_INIT_POINTER(dst->fence_excl, new);
-	RCU_INIT_POINTER(dst->fence, dst_list);
+	excl = rcu_replace_pointer(dst->fence_excl, excl, dma_resv_held(dst));
+	list = rcu_replace_pointer(dst->fence, list, dma_resv_held(dst));
 	write_seqcount_end(&dst->seq);
 
-	dma_resv_list_free(src_list);
-	dma_fence_put(old);
+	dma_resv_list_free(list);
+	dma_fence_put(excl);
 
 	return 0;
 }