[Intel-gfx] [PATCH 6/7] dma-buf/sw-sync: Fix locking around sync_timeline lists

Sean Paul seanpaul at chromium.org
Thu Jun 29 17:22:10 UTC 2017


On Thu, Jun 29, 2017 at 01:59:29PM +0100, Chris Wilson wrote:
> The sync_pt were not adding themselves atomically to the timeline lists,
> corruption imminent.  Only a single list is required to track the
> unsignaled sync_pt, so reduce it and rename the lock more appropriately
> along with using idiomatic names to distinguish a list from links along
> it.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Sumit Semwal <sumit.semwal at linaro.org>
> Cc: Sean Paul <seanpaul at chromium.org>
> Cc: Gustavo Padovan <gustavo at padovan.org>
> ---
>  drivers/dma-buf/sw_sync.c    | 39 ++++++++++++++-------------------------
>  drivers/dma-buf/sync_debug.c |  9 ++++-----
>  drivers/dma-buf/sync_debug.h | 21 ++++++++-------------
>  3 files changed, 26 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
> index 6effa1ce010e..e51fe11bbbea 100644
> --- a/drivers/dma-buf/sw_sync.c
> +++ b/drivers/dma-buf/sw_sync.c
> @@ -96,9 +96,8 @@ static struct sync_timeline *sync_timeline_create(const char *name)
>  	obj->context = dma_fence_context_alloc(1);
>  	strlcpy(obj->name, name, sizeof(obj->name));
>  
> -	INIT_LIST_HEAD(&obj->child_list_head);
> -	INIT_LIST_HEAD(&obj->active_list_head);
> -	spin_lock_init(&obj->child_list_lock);
> +	INIT_LIST_HEAD(&obj->pt_list);
> +	spin_lock_init(&obj->lock);
>  
>  	sync_timeline_debug_add(obj);
>  
> @@ -139,17 +138,15 @@ static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
>  
>  	trace_sync_timeline(obj);
>  
> -	spin_lock_irq(&obj->child_list_lock);
> +	spin_lock_irq(&obj->lock);
>  
>  	obj->value += inc;
>  
> -	list_for_each_entry_safe(pt, next, &obj->active_list_head,
> -				 active_list) {
> +	list_for_each_entry_safe(pt, next, &obj->pt_list, link)
>  		if (dma_fence_is_signaled_locked(&pt->base))
> -			list_del_init(&pt->active_list);
> -	}
> +			list_del_init(&pt->link);
>  
> -	spin_unlock_irq(&obj->child_list_lock);
> +	spin_unlock_irq(&obj->lock);
>  }
>  
>  /**
> @@ -171,15 +168,15 @@ static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
>  	if (!pt)
>  		return NULL;
>  
> -	spin_lock_irq(&obj->child_list_lock);
> -
>  	sync_timeline_get(obj);
> -	dma_fence_init(&pt->base, &timeline_fence_ops, &obj->child_list_lock,
> +	dma_fence_init(&pt->base, &timeline_fence_ops, &obj->lock,
>  		       obj->context, value);
> -	list_add_tail(&pt->child_list, &obj->child_list_head);
> -	INIT_LIST_HEAD(&pt->active_list);
> +	INIT_LIST_HEAD(&pt->link);
>  
> -	spin_unlock_irq(&obj->child_list_lock);
> +	spin_lock_irq(&obj->lock);
> +	if (!dma_fence_is_signaled_locked(&pt->base))
> +		list_add_tail(&pt->link, &obj->pt_list);
> +	spin_unlock_irq(&obj->lock);
>  
>  	return pt;
>  }
> @@ -204,9 +201,8 @@ static void timeline_fence_release(struct dma_fence *fence)
>  
>  	spin_lock_irqsave(fence->lock, flags);
>  
> -	list_del(&pt->child_list);
> -	if (!list_empty(&pt->active_list))
> -		list_del(&pt->active_list);
> +	if (!list_empty(&pt->link))
> +		list_del(&pt->link);
>  
>  	spin_unlock_irqrestore(fence->lock, flags);
>  
> @@ -223,13 +219,6 @@ static bool timeline_fence_signaled(struct dma_fence *fence)
>  
>  static bool timeline_fence_enable_signaling(struct dma_fence *fence)
>  {
> -	struct sync_pt *pt = dma_fence_to_sync_pt(fence);
> -	struct sync_timeline *parent = dma_fence_parent(fence);
> -
> -	if (timeline_fence_signaled(fence))
> -		return false;
> -
> -	list_add_tail(&pt->active_list, &parent->active_list_head);
>  	return true;

Shouldn't you still return false if the fence is already signaled?

>  }
>  
> diff --git a/drivers/dma-buf/sync_debug.c b/drivers/dma-buf/sync_debug.c
> index 0e91632248ba..2264a075f6a9 100644
> --- a/drivers/dma-buf/sync_debug.c
> +++ b/drivers/dma-buf/sync_debug.c
> @@ -119,13 +119,12 @@ static void sync_print_obj(struct seq_file *s, struct sync_timeline *obj)
>  
>  	seq_printf(s, "%s: %d\n", obj->name, obj->value);
>  
> -	spin_lock_irq(&obj->child_list_lock);
> -	list_for_each(pos, &obj->child_list_head) {
> -		struct sync_pt *pt =
> -			container_of(pos, struct sync_pt, child_list);
> +	spin_lock_irq(&obj->lock);
> +	list_for_each(pos, &obj->pt_list) {
> +		struct sync_pt *pt = container_of(pos, struct sync_pt, link);
>  		sync_print_fence(s, &pt->base, false);
>  	}
> -	spin_unlock_irq(&obj->child_list_lock);
> +	spin_unlock_irq(&obj->lock);
>  }
>  
>  static void sync_print_sync_file(struct seq_file *s,
> diff --git a/drivers/dma-buf/sync_debug.h b/drivers/dma-buf/sync_debug.h
> index 26fe8b9907b3..899ba0e19fd3 100644
> --- a/drivers/dma-buf/sync_debug.h
> +++ b/drivers/dma-buf/sync_debug.h
> @@ -24,42 +24,37 @@
>   * struct sync_timeline - sync object
>   * @kref:		reference count on fence.
>   * @name:		name of the sync_timeline. Useful for debugging
> - * @child_list_head:	list of children sync_pts for this sync_timeline
> - * @child_list_lock:	lock protecting @child_list_head and fence.status
> - * @active_list_head:	list of active (unsignaled/errored) sync_pts
> + * @lock:		lock protecting @child_list_head and fence.status

s/child_list/pt_list/

> + * @pt_list:		list of active (unsignaled/errored) sync_pts
>   * @sync_timeline_list:	membership in global sync_timeline_list
>   */
>  struct sync_timeline {
>  	struct kref		kref;
>  	char			name[32];
>  
> -	/* protected by child_list_lock */
> +	/* protected by lock */
>  	u64			context;
>  	int			value;
>  
> -	struct list_head	child_list_head;
> -	spinlock_t		child_list_lock;
> -
> -	struct list_head	active_list_head;
> +	struct list_head	pt_list;
> +	spinlock_t		lock;
>  
>  	struct list_head	sync_timeline_list;
>  };
>  
>  static inline struct sync_timeline *dma_fence_parent(struct dma_fence *fence)
>  {
> -	return container_of(fence->lock, struct sync_timeline, child_list_lock);
> +	return container_of(fence->lock, struct sync_timeline, lock);
>  }
>  
>  /**
>   * struct sync_pt - sync_pt object
>   * @base: base fence object
> - * @child_list: sync timeline child's list
> - * @active_list: sync timeline active child's list
> + * @link: link on the sync timeline's list
>   */
>  struct sync_pt {
>  	struct dma_fence base;
> -	struct list_head child_list;
> -	struct list_head active_list;
> +	struct list_head link;
>  };
>  
>  #ifdef CONFIG_SW_SYNC
> -- 
> 2.13.1

-- 
Sean Paul, Software Engineer, Google / Chromium OS


More information about the Intel-gfx mailing list