[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
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