1 files changed, 166 insertions, 2 deletions

diff --git a/drivers/base/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 840c7fa80983..f3014c448e1e 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -25,10 +25,13 @@
 #include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/dma-buf.h>
+#include <linux/fence.h>
 #include <linux/anon_inodes.h>
 #include <linux/export.h>
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
+#include <linux/poll.h>
+#include <linux/reservation.h>
 
 static inline int is_dma_buf_file(struct file *);
 
@@ -50,12 +53,25 @@ static int dma_buf_release(struct inode *inode, struct file *file)
 
 	BUG_ON(dmabuf->vmapping_counter);
 
+	/*
+	 * Any fences that a dma-buf poll can wait on should be signaled
+	 * before releasing dma-buf. This is the responsibility of each
+	 * driver that uses the reservation objects.
+	 *
+	 * If you hit this BUG() it means someone dropped their ref to the
+	 * dma-buf while still having pending operation to the buffer.
+	 */
+	BUG_ON(dmabuf->cb_shared.active || dmabuf->cb_excl.active);
+
 	dmabuf->ops->release(dmabuf);
 
 	mutex_lock(&db_list.lock);
 	list_del(&dmabuf->list_node);
 	mutex_unlock(&db_list.lock);
 
+	if (dmabuf->resv == (struct reservation_object *)&dmabuf[1])
+		reservation_object_fini(dmabuf->resv);
+
 	kfree(dmabuf);
 	return 0;
 }
@@ -103,10 +119,141 @@ static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
 	return base + offset;
 }
 
+static void dma_buf_poll_cb(struct fence *fence, struct fence_cb *cb)
+{
+	struct dma_buf_poll_cb_t *dcb = (struct dma_buf_poll_cb_t *)cb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&dcb->poll->lock, flags);
+	wake_up_locked_poll(dcb->poll, dcb->active);
+	dcb->active = 0;
+	spin_unlock_irqrestore(&dcb->poll->lock, flags);
+}
+
+static unsigned int dma_buf_poll(struct file *file, poll_table *poll)
+{
+	struct dma_buf *dmabuf;
+	struct reservation_object *resv;
+	struct reservation_object_list *fobj;
+	struct fence *fence_excl;
+	unsigned long events;
+	unsigned shared_count, seq;
+
+	dmabuf = file->private_data;
+	if (!dmabuf || !dmabuf->resv)
+		return POLLERR;
+
+	resv = dmabuf->resv;
+
+	poll_wait(file, &dmabuf->poll, poll);
+
+	events = poll_requested_events(poll) & (POLLIN | POLLOUT);
+	if (!events)
+		return 0;
+
+retry:
+	seq = read_seqcount_begin(&resv->seq);
+	rcu_read_lock();
+
+	fobj = rcu_dereference(resv->fence);
+	if (fobj)
+		shared_count = fobj->shared_count;
+	else
+		shared_count = 0;
+	fence_excl = rcu_dereference(resv->fence_excl);
+	if (read_seqcount_retry(&resv->seq, seq)) {
+		rcu_read_unlock();
+		goto retry;
+	}
+
+	if (fence_excl && (!(events & POLLOUT) || shared_count == 0)) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_excl;
+		unsigned long pevents = POLLIN;
+
+		if (shared_count == 0)
+			pevents |= POLLOUT;
+
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active) {
+			dcb->active |= pevents;
+			events &= ~pevents;
+		} else
+			dcb->active = pevents;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (events & pevents) {
+			if (!fence_get_rcu(fence_excl)) {
+				/* force a recheck */
+				events &= ~pevents;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			} else if (!fence_add_callback(fence_excl, &dcb->cb,
+						       dma_buf_poll_cb)) {
+				events &= ~pevents;
+				fence_put(fence_excl);
+			} else {
+				/*
+				 * No callback queued, wake up any additional
+				 * waiters.
+				 */
+				fence_put(fence_excl);
+				dma_buf_poll_cb(NULL, &dcb->cb);
+			}
+		}
+	}
+
+	if ((events & POLLOUT) && shared_count > 0) {
+		struct dma_buf_poll_cb_t *dcb = &dmabuf->cb_shared;
+		int i;
+
+		/* Only queue a new callback if no event has fired yet */
+		spin_lock_irq(&dmabuf->poll.lock);
+		if (dcb->active)
+			events &= ~POLLOUT;
+		else
+			dcb->active = POLLOUT;
+		spin_unlock_irq(&dmabuf->poll.lock);
+
+		if (!(events & POLLOUT))
+			goto out;
+
+		for (i = 0; i < shared_count; ++i) {
+			struct fence *fence = rcu_dereference(fobj->shared[i]);
+
+			if (!fence_get_rcu(fence)) {
+				/*
+				 * fence refcount dropped to zero, this means
+				 * that fobj has been freed
+				 *
+				 * call dma_buf_poll_cb and force a recheck!
+				 */
+				events &= ~POLLOUT;
+				dma_buf_poll_cb(NULL, &dcb->cb);
+				break;
+			}
+			if (!fence_add_callback(fence, &dcb->cb,
+						dma_buf_poll_cb)) {
+				fence_put(fence);
+				events &= ~POLLOUT;
+				break;
+			}
+			fence_put(fence);
+		}
+
+		/* No callback queued, wake up any additional waiters. */
+		if (i == shared_count)
+			dma_buf_poll_cb(NULL, &dcb->cb);
+	}
+
+out:
+	rcu_read_unlock();
+	return events;
+}
+
 static const struct file_operations dma_buf_fops = {
 	.release	= dma_buf_release,
 	.mmap		= dma_buf_mmap_internal,
 	.llseek		= dma_buf_llseek,
+	.poll		= dma_buf_poll,
 };
 
 /*
@@ -128,6 +275,7 @@ static inline int is_dma_buf_file(struct file *file)
  * @size:	[in]	Size of the buffer
  * @flags:	[in]	mode flags for the file.
  * @exp_name:	[in]	name of the exporting module - useful for debugging.
+ * @resv:	[in]	reservation-object, NULL to allocate default one.
  *
  * Returns, on success, a newly created dma_buf object, which wraps the
  * supplied private data and operations for dma_buf_ops. On either missing
@@ -135,10 +283,17 @@ static inline int is_dma_buf_file(struct file *file)
  *
  */
 struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
-				size_t size, int flags, const char *exp_name)
+				size_t size, int flags, const char *exp_name,
+				struct reservation_object *resv)
 {
 	struct dma_buf *dmabuf;
 	struct file *file;
+	size_t alloc_size = sizeof(struct dma_buf);
+	if (!resv)
+		alloc_size += sizeof(struct reservation_object);
+	else
+		/* prevent &dma_buf[1] == dma_buf->resv */
+		alloc_size += 1;
 
 	if (WARN_ON(!priv || !ops
 			  || !ops->map_dma_buf
@@ -150,7 +305,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
 		return ERR_PTR(-EINVAL);
 	}
 
-	dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
+	dmabuf = kzalloc(alloc_size, GFP_KERNEL);
 	if (dmabuf == NULL)
 		return ERR_PTR(-ENOMEM);
 
@@ -158,6 +313,15 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops,
 	dmabuf->ops = ops;
 	dmabuf->size = size;
 	dmabuf->exp_name = exp_name;
+	init_waitqueue_head(&dmabuf->poll);
+	dmabuf->cb_excl.poll = dmabuf->cb_shared.poll = &dmabuf->poll;
+	dmabuf->cb_excl.active = dmabuf->cb_shared.active = 0;
+
+	if (!resv) {
+		resv = (struct reservation_object *)&dmabuf[1];
+		reservation_object_init(resv);
+	}
+	dmabuf->resv = resv;
 
 	file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
 	if (IS_ERR(file)) {