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Diffstat (limited to 'include/linux/dma-fence.h')
-rw-r--r--include/linux/dma-fence.h34
1 files changed, 27 insertions, 7 deletions
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 05d29dbc7e62..3347c54f3a87 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -63,15 +63,35 @@ struct dma_fence_cb;
* been completed, or never called at all.
*/
struct dma_fence {
- struct kref refcount;
- const struct dma_fence_ops *ops;
- struct rcu_head rcu;
- struct list_head cb_list;
spinlock_t *lock;
+ const struct dma_fence_ops *ops;
+ /*
+ * We clear the callback list on kref_put so that by the time we
+ * release the fence it is unused. No one should be adding to the
+ * cb_list that they don't themselves hold a reference for.
+ *
+ * The lifetime of the timestamp is similarly tied to both the
+ * rcu freelist and the cb_list. The timestamp is only set upon
+ * signaling while simultaneously notifying the cb_list. Ergo, we
+ * only use either the cb_list of timestamp. Upon destruction,
+ * neither are accessible, and so we can use the rcu. This means
+ * that the cb_list is *only* valid until the signal bit is set,
+ * and to read either you *must* hold a reference to the fence,
+ * and not just the rcu_read_lock.
+ *
+ * Listed in chronological order.
+ */
+ union {
+ struct list_head cb_list;
+ /* @cb_list replaced by @timestamp on dma_fence_signal() */
+ ktime_t timestamp;
+ /* @timestamp replaced by @rcu on dma_fence_release() */
+ struct rcu_head rcu;
+ };
u64 context;
u64 seqno;
unsigned long flags;
- ktime_t timestamp;
+ struct kref refcount;
int error;
};
@@ -273,7 +293,7 @@ static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
}
/**
- * dma_fence_get_rcu - get a fence from a reservation_object_list with
+ * dma_fence_get_rcu - get a fence from a dma_resv_list with
* rcu read lock
* @fence: fence to increase refcount of
*
@@ -297,7 +317,7 @@ static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
* so long as the caller is using RCU on the pointer to the fence.
*
* An alternative mechanism is to employ a seqlock to protect a bunch of
- * fences, such as used by struct reservation_object. When using a seqlock,
+ * fences, such as used by struct dma_resv. When using a seqlock,
* the seqlock must be taken before and checked after a reference to the
* fence is acquired (as shown here).
*