[RFC,2/3] dma-buf-mgr: multiple dma-buf synchronization (v2)

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 1e7723b..819281a 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -10,7 +10,8 @@  obj-$(CONFIG_CMA) += dma-contiguous.o
 obj-y			+= power/
 obj-$(CONFIG_HAS_DMA)	+= dma-mapping.o
 obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
-obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o dma-fence.o dma-bikeshed-fence.o
+obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o dma-fence.o dma-buf-mgr.o \
+			   dma-bikeshed-fence.o
 obj-$(CONFIG_ISA)	+= isa.o
 obj-$(CONFIG_FW_LOADER)	+= firmware_class.o
 obj-$(CONFIG_NUMA)	+= node.o
diff --git a/drivers/base/dma-buf-mgr.c b/drivers/base/dma-buf-mgr.c
new file mode 100644
index 0000000..71b5f96
--- /dev/null
+++ b/drivers/base/dma-buf-mgr.c
@@ -0,0 +1,230 @@ 
+/*
+ * Copyright (C) 2012 Canonical Ltd
+ *
+ * Based on ttm_bo.c which bears the following copyright notice,
+ * but is dual licensed:
+ *
+ * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+ * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+ * USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+/*
+ * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
+ */
+
+
+#include <linux/dma-buf-mgr.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+
+static void dmabufmgr_backoff_reservation_locked(struct list_head *list)
+{
+	struct dmabufmgr_validate *entry;
+
+	list_for_each_entry(entry, list, head) {
+		struct dma_buf *bo = entry->bo;
+		if (!entry->reserved)
+			continue;
+		entry->reserved = false;
+
+		entry->num_fences = 0;
+
+		atomic_set(&bo->reserved, 0);
+		wake_up_all(&bo->event_queue);
+	}
+}
+
+static int
+dmabufmgr_wait_unreserved_locked(struct list_head *list,
+				    struct dma_buf *bo)
+{
+	int ret;
+
+	spin_unlock(&dma_buf_reserve_lock);
+	ret = dma_buf_wait_unreserved(bo, true);
+	spin_lock(&dma_buf_reserve_lock);
+	if (unlikely(ret != 0))
+		dmabufmgr_backoff_reservation_locked(list);
+	return ret;
+}
+
+void
+dmabufmgr_backoff_reservation(struct list_head *list)
+{
+	if (list_empty(list))
+		return;
+
+	spin_lock(&dma_buf_reserve_lock);
+	dmabufmgr_backoff_reservation_locked(list);
+	spin_unlock(&dma_buf_reserve_lock);
+}
+EXPORT_SYMBOL_GPL(dmabufmgr_backoff_reservation);
+
+int
+dmabufmgr_reserve_buffers(struct list_head *list)
+{
+	struct dmabufmgr_validate *entry;
+	int ret;
+	u32 val_seq;
+
+	if (list_empty(list))
+		return 0;
+
+	list_for_each_entry(entry, list, head) {
+		entry->reserved = false;
+		entry->num_fences = 0;
+	}
+
+retry:
+	spin_lock(&dma_buf_reserve_lock);
+	val_seq = atomic_inc_return(&dma_buf_reserve_counter);
+
+	list_for_each_entry(entry, list, head) {
+		struct dma_buf *bo = entry->bo;
+
+retry_this_bo:
+		ret = dma_buf_reserve_locked(bo, true, true, true, val_seq);
+		switch (ret) {
+		case 0:
+			break;
+		case -EBUSY:
+			ret = dmabufmgr_wait_unreserved_locked(list, bo);
+			if (unlikely(ret != 0)) {
+				spin_unlock(&dma_buf_reserve_lock);
+				return ret;
+			}
+			goto retry_this_bo;
+		case -EAGAIN:
+			dmabufmgr_backoff_reservation_locked(list);
+			spin_unlock(&dma_buf_reserve_lock);
+			ret = dma_buf_wait_unreserved(bo, true);
+			if (unlikely(ret != 0))
+				return ret;
+			goto retry;
+		default:
+			dmabufmgr_backoff_reservation_locked(list);
+			spin_unlock(&dma_buf_reserve_lock);
+			return ret;
+		}
+
+		entry->reserved = true;
+
+		if (entry->shared &&
+		    bo->fence_shared_count == DMA_BUF_MAX_SHARED_FENCE) {
+			WARN_ON_ONCE(1);
+			dmabufmgr_backoff_reservation_locked(list);
+			spin_unlock(&dma_buf_reserve_lock);
+			return -EINVAL;
+		}
+
+		if (!entry->shared && bo->fence_shared_count) {
+			entry->num_fences = bo->fence_shared_count;
+			BUILD_BUG_ON(sizeof(entry->fences) != sizeof(bo->fence_shared));
+			memcpy(entry->fences, bo->fence_shared, sizeof(bo->fence_shared));
+		} else if (bo->fence_excl) {
+			entry->num_fences = 1;
+			entry->fences[0] = bo->fence_excl;
+		} else
+			entry->num_fences = 0;
+	}
+	spin_unlock(&dma_buf_reserve_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dmabufmgr_reserve_buffers);
+
+static int
+dmabufmgr_wait_single(struct dmabufmgr_validate *val, bool intr, bool lazy,
+		unsigned long timeout)
+{
+	int i, ret = 0;
+
+	for (i = 0; i < val->num_fences && !ret; i++)
+		ret = dma_fence_wait(val->fences[i], intr, timeout);
+	return ret;
+}
+
+int
+dmabufmgr_wait_completed_cpu(struct list_head *list, bool intr, bool lazy)
+{
+	struct dmabufmgr_validate *entry;
+	unsigned long timeout = jiffies + 4 * HZ;
+	int ret;
+
+	list_for_each_entry(entry, list, head) {
+		ret = dmabufmgr_wait_single(entry, intr, lazy, timeout);
+		if (ret && ret != -ERESTARTSYS)
+			pr_err("waiting returns %i\n", ret);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dmabufmgr_wait_completed_cpu);
+
+void
+dmabufmgr_fence_buffer_objects(struct dma_fence *fence, struct list_head *list)
+{
+	struct dmabufmgr_validate *entry;
+	struct dma_buf *bo;
+
+	if (list_empty(list) || WARN_ON(!fence))
+		return;
+
+	/* Until deferred fput hits mainline, release old things here */
+	list_for_each_entry(entry, list, head) {
+		bo = entry->bo;
+
+		if (!entry->shared) {
+			int i;
+			for (i = 0; i < bo->fence_shared_count; ++i) {
+				dma_fence_put(bo->fence_shared[i]);
+				bo->fence_shared[i] = NULL;
+			}
+			bo->fence_shared_count = 0;
+			if (bo->fence_excl) {
+				dma_fence_put(bo->fence_excl);
+				bo->fence_excl = NULL;
+			}
+		}
+
+		entry->reserved = false;
+	}
+
+	spin_lock(&dma_buf_reserve_lock);
+
+	list_for_each_entry(entry, list, head) {
+		bo = entry->bo;
+
+		dma_fence_get(fence);
+		if (entry->shared)
+			bo->fence_shared[bo->fence_shared_count++] = fence;
+		else
+			bo->fence_excl = fence;
+
+		dma_buf_unreserve_locked(bo);
+	}
+
+	spin_unlock(&dma_buf_reserve_lock);
+}
+EXPORT_SYMBOL_GPL(dmabufmgr_fence_buffer_objects);
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
index 757ee20..6e76baf 100644
--- a/drivers/base/dma-buf.c
+++ b/drivers/base/dma-buf.c
@@ -27,12 +27,17 @@ 
 #include <linux/dma-buf.h>
 #include <linux/anon_inodes.h>
 #include <linux/export.h>
+#include <linux/sched.h>
+
+atomic_t dma_buf_reserve_counter = ATOMIC_INIT(1);
+DEFINE_SPINLOCK(dma_buf_reserve_lock);
 
 static inline int is_dma_buf_file(struct file *);
 
 static int dma_buf_release(struct inode *inode, struct file *file)
 {
 	struct dma_buf *dmabuf;
+	int i;
 
 	if (!is_dma_buf_file(file))
 		return -EINVAL;
@@ -40,6 +45,15 @@  static int dma_buf_release(struct inode *inode, struct file *file)
 	dmabuf = file->private_data;
 
 	dmabuf->ops->release(dmabuf);
+
+	BUG_ON(waitqueue_active(&dmabuf->event_queue));
+	BUG_ON(atomic_read(&dmabuf->reserved));
+
+	if (dmabuf->fence_excl)
+		dma_fence_put(dmabuf->fence_excl);
+	for (i = 0; i < dmabuf->fence_shared_count; ++i)
+		dma_fence_put(dmabuf->fence_shared[i]);
+
 	kfree(dmabuf);
 	return 0;
 }
@@ -119,6 +133,7 @@  struct dma_buf *dma_buf_export(void *priv, const struct dma_buf_ops *ops,
 
 	mutex_init(&dmabuf->lock);
 	INIT_LIST_HEAD(&dmabuf->attachments);
+	init_waitqueue_head(&dmabuf->event_queue);
 
 	return dmabuf;
 }
@@ -566,3 +581,101 @@  void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
 		dmabuf->ops->vunmap(dmabuf, vaddr);
 }
 EXPORT_SYMBOL_GPL(dma_buf_vunmap);
+
+int
+dma_buf_reserve_locked(struct dma_buf *dmabuf, bool interruptible,
+		       bool no_wait, bool use_sequence, u32 sequence)
+{
+	int ret;
+
+	while (unlikely(atomic_cmpxchg(&dmabuf->reserved, 0, 1) != 0)) {
+		/**
+		 * Deadlock avoidance for multi-dmabuf reserving.
+		 */
+		if (use_sequence && dmabuf->seq_valid) {
+			/**
+			 * We've already reserved this one.
+			 */
+			if (unlikely(sequence == dmabuf->val_seq))
+				return -EDEADLK;
+			/**
+			 * Already reserved by a thread that will not back
+			 * off for us. We need to back off.
+			 */
+			if (unlikely(sequence - dmabuf->val_seq < (1 << 31)))
+				return -EAGAIN;
+		}
+
+		if (no_wait)
+			return -EBUSY;
+
+		spin_unlock(&dma_buf_reserve_lock);
+		ret = dma_buf_wait_unreserved(dmabuf, interruptible);
+		spin_lock(&dma_buf_reserve_lock);
+
+		if (unlikely(ret))
+			return ret;
+	}
+
+	if (use_sequence) {
+		/**
+		 * Wake up waiters that may need to recheck for deadlock,
+		 * if we decreased the sequence number.
+		 */
+		if (unlikely((dmabuf->val_seq - sequence < (1 << 31))
+			     || !dmabuf->seq_valid))
+			wake_up_all(&dmabuf->event_queue);
+
+		dmabuf->val_seq = sequence;
+		dmabuf->seq_valid = true;
+	} else {
+		dmabuf->seq_valid = false;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dma_buf_reserve_locked);
+
+int
+dma_buf_reserve(struct dma_buf *dmabuf, bool interruptible, bool no_wait,
+		bool use_sequence, u32 sequence)
+{
+	int ret;
+
+	spin_lock(&dma_buf_reserve_lock);
+	ret = dma_buf_reserve_locked(dmabuf, interruptible, no_wait,
+				     use_sequence, sequence);
+	spin_unlock(&dma_buf_reserve_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dma_buf_reserve);
+
+int
+dma_buf_wait_unreserved(struct dma_buf *dmabuf, bool interruptible)
+{
+	if (interruptible) {
+		return wait_event_interruptible(dmabuf->event_queue,
+				atomic_read(&dmabuf->reserved) == 0);
+	} else {
+		wait_event(dmabuf->event_queue,
+			   atomic_read(&dmabuf->reserved) == 0);
+		return 0;
+	}
+}
+EXPORT_SYMBOL_GPL(dma_buf_wait_unreserved);
+
+void dma_buf_unreserve_locked(struct dma_buf *dmabuf)
+{
+	atomic_set(&dmabuf->reserved, 0);
+	wake_up_all(&dmabuf->event_queue);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unreserve_locked);
+
+void dma_buf_unreserve(struct dma_buf *dmabuf)
+{
+	spin_lock(&dma_buf_reserve_lock);
+	dma_buf_unreserve_locked(dmabuf);
+	spin_unlock(&dma_buf_reserve_lock);
+}
+EXPORT_SYMBOL_GPL(dma_buf_unreserve);
diff --git a/drivers/base/dma-fence.c b/drivers/base/dma-fence.c
index 6798dc4..7fa4c74 100644
--- a/drivers/base/dma-fence.c
+++ b/drivers/base/dma-fence.c
@@ -20,6 +20,7 @@ 
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/export.h>
+#include <linux/dma-buf.h>
 #include <linux/dma-fence.h>
 
 /**
diff --git a/include/linux/dma-buf-mgr.h b/include/linux/dma-buf-mgr.h
new file mode 100644
index 0000000..64baab1
--- /dev/null
+++ b/include/linux/dma-buf-mgr.h
@@ -0,0 +1,97 @@ 
+/*
+ * Header file for dma buffer sharing framework.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal@ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd@arndb.de>, Rob Clark <rob@ti.com> and
+ * Daniel Vetter <daniel@ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __DMA_BUF_MGR_H__
+#define __DMA_BUF_MGR_H__
+
+#include <linux/dma-buf.h>
+#include <linux/list.h>
+
+/** based on ttm_execbuf_util
+ */
+struct dmabufmgr_validate {
+	/* Input parameters, set before reserve */
+	struct list_head head;
+	struct dma_buf *bo;
+	void *priv;
+	bool shared;
+
+	/* for internal use */
+	bool reserved;
+	/* fences to wait on, if shared, last exclusive fence
+	 * if exclusive, last shared fences (if non-null), or
+	 * last exclusive fence
+	 */
+	unsigned num_fences;
+	struct dma_fence *fences[DMA_BUF_MAX_SHARED_FENCE];
+};
+
+#ifdef CONFIG_DMA_SHARED_BUFFER
+
+/** reserve a linked list of struct dmabufmgr_validate entries */
+extern int
+dmabufmgr_reserve_buffers(struct list_head *list);
+
+/** Undo reservation */
+extern void
+dmabufmgr_backoff_reservation(struct list_head *list);
+
+/** Commit reservation */
+extern void
+dmabufmgr_fence_buffer_objects(struct dma_fence *fence, struct list_head *list);
+
+/** Wait for completion on cpu
+ * intr: interruptible wait
+ * lazy: try once every tick instead of busywait
+ */
+extern int
+dmabufmgr_wait_completed_cpu(struct list_head *list, bool intr, bool lazy);
+
+#else /* CONFIG_DMA_SHARED_BUFFER */
+
+/** reserve a linked list of struct dmabufmgr_validate entries */
+static inline int
+dmabufmgr_reserve_buffers(struct list_head *list)
+{
+	return list_empty(list) ? 0 : -ENODEV;
+}
+
+/** Undo reservation */
+static inline void
+dmabufmgr_backoff_reservation(struct list_head *list)
+{}
+
+/** Commit reservation */
+static inline void
+dmabufmgr_fence_buffer_objects(struct dma_fence *fence, struct list_head *list)
+{}
+
+static inline int
+dmabufmgr_wait_completed_cpu(struct list_head *list, bool intr, bool lazy)
+{
+	return list_empty(list) ? 0 : -ENODEV;
+}
+
+#endif /* CONFIG_DMA_SHARED_BUFFER */
+
+#endif /* __DMA_BUF_MGR_H__ */
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 9533b9b..d3d76e5 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -35,6 +35,13 @@  struct device;
 struct dma_buf;
 struct dma_buf_attachment;
 
+#include <linux/dma-fence.h>
+
+extern atomic_t dma_buf_reserve_counter;
+extern spinlock_t dma_buf_reserve_lock;
+
+#define DMA_BUF_MAX_SHARED_FENCE 8
+
 /**
  * struct dma_buf_ops - operations possible on struct dma_buf
  * @attach: [optional] allows different devices to 'attach' themselves to the
@@ -113,6 +120,8 @@  struct dma_buf_ops {
  * @attachments: list of dma_buf_attachment that denotes all devices attached.
  * @ops: dma_buf_ops associated with this buffer object.
  * @priv: exporter specific private data for this buffer object.
+ * @bufmgr_entry: used by dmabufmgr
+ * @bufdev: used by dmabufmgr
  */
 struct dma_buf {
 	size_t size;
@@ -122,6 +131,18 @@  struct dma_buf {
 	/* mutex to serialize list manipulation and attach/detach */
 	struct mutex lock;
 	void *priv;
+
+	/** event queue for waking up when this dmabuf becomes unreserved */
+	wait_queue_head_t event_queue;
+
+	atomic_t reserved;
+
+	/** These require dma_buf_reserve to be called before modification */
+	bool seq_valid;
+	u32 val_seq;
+	struct dma_fence *fence_excl;
+	struct dma_fence *fence_shared[DMA_BUF_MAX_SHARED_FENCE];
+	u32 fence_shared_count;
 };
 
 /**
@@ -188,6 +209,14 @@  int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
 		 unsigned long);
 void *dma_buf_vmap(struct dma_buf *);
 void dma_buf_vunmap(struct dma_buf *, void *vaddr);
+int dma_buf_reserve_locked(struct dma_buf *, bool intr, bool no_wait,
+			   bool use_seq, u32 seq);
+int dma_buf_reserve(struct dma_buf *, bool intr, bool no_wait,
+		    bool use_seq, u32 seq);
+int dma_buf_wait_unreserved(struct dma_buf *, bool interruptible);
+void dma_buf_unreserve_locked(struct dma_buf *);
+void dma_buf_unreserve(struct dma_buf *);
+
 #else
 
 static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
@@ -300,6 +329,8 @@  static inline void *dma_buf_vmap(struct dma_buf *dmabuf)
 static inline void dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
 {
 }
+
+// TODO
 #endif /* CONFIG_DMA_SHARED_BUFFER */
 
 #endif /* __DMA_BUF_H__ */
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 648f136..8938f48 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -24,7 +24,7 @@ 
 #include <linux/list.h>
 #include <linux/wait.h>
 #include <linux/list.h>
-#include <linux/dma-buf.h>
+#include <linux/kref.h>
 
 struct dma_fence;
 struct dma_fence_ops;