dma-buf/sw-sync: Use an rbtree to sort fences in the timeline

Reduce the list iteration when incrementing the timeline by storing the
fences in increasing order.

v2: Prevent spinlock recursion on free during create
v3: Fixup rebase conflict inside comments that escaped the compiler.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170629211253.22766-1-chris@chris-wilson.co.uk

2 files changed, 48 insertions, 6 deletions

diff --git a/drivers/dma-buf/sw_sync.c b/drivers/dma-buf/sw_sync.c
index f20d18c421a3..af1bc84802e5 100644
--- a/drivers/dma-buf/sw_sync.c
+++ b/drivers/dma-buf/sw_sync.c
@@ -96,6 +96,7 @@ static struct sync_timeline *sync_timeline_create(const char *name)
         obj->context = dma_fence_context_alloc(1);
         strlcpy(obj->name, name, sizeof(obj->name));
 
+        obj->pt_tree = RB_ROOT;
         INIT_LIST_HEAD(&obj->pt_list);
         spin_lock_init(&obj->lock);
 
@@ -142,9 +143,13 @@ static void sync_timeline_signal(struct sync_timeline *obj, unsigned int inc)
 
         obj->value += inc;
 
-        list_for_each_entry_safe(pt, next, &obj->pt_list, link)
-                if (dma_fence_is_signaled_locked(&pt->base))
-                        list_del_init(&pt->link);
+        list_for_each_entry_safe(pt, next, &obj->pt_list, link) {
+                if (!dma_fence_is_signaled_locked(&pt->base))
+                        break;
+
+                list_del_init(&pt->link);
+                rb_erase(&pt->node, &obj->pt_tree);
+        }
 
         spin_unlock_irq(&obj->lock);
 }
@@ -174,8 +179,38 @@ static struct sync_pt *sync_pt_create(struct sync_timeline *obj,
         INIT_LIST_HEAD(&pt->link);
 
         spin_lock_irq(&obj->lock);
-        if (!dma_fence_is_signaled_locked(&pt->base))
-                list_add_tail(&pt->link, &obj->pt_list);
+        if (!dma_fence_is_signaled_locked(&pt->base)) {
+                struct rb_node **p = &obj->pt_tree.rb_node;
+                struct rb_node *parent = NULL;
+
+                while (*p) {
+                        struct sync_pt *other;
+                        int cmp;
+
+                        parent = *p;
+                        other = rb_entry(parent, typeof(*pt), node);
+                        cmp = value - other->base.seqno;
+                        if (cmp > 0) {
+                                p = &parent->rb_right;
+                        } else if (cmp < 0) {
+                                p = &parent->rb_left;
+                        } else {
+                                if (dma_fence_get_rcu(&other->base)) {
+                                        dma_fence_put(&pt->base);
+                                        pt = other;
+                                        goto unlock;
+                                }
+                                p = &parent->rb_left;
+                        }
+                }
+                rb_link_node(&pt->node, parent, p);
+                rb_insert_color(&pt->node, &obj->pt_tree);
+
+                parent = rb_next(&pt->node);
+                list_add_tail(&pt->link,
+                              parent ? &rb_entry(parent, typeof(*pt), node)->link : &obj->pt_list);
+        }
+unlock:
         spin_unlock_irq(&obj->lock);
 
         return pt;
@@ -202,8 +237,10 @@ static void timeline_fence_release(struct dma_fence *fence)
                 unsigned long flags;
 
                 spin_lock_irqsave(fence->lock, flags);
-                if (!list_empty(&pt->link))
+                if (!list_empty(&pt->link)) {
                         list_del(&pt->link);
+                        rb_erase(&pt->node, &parent->pt_tree);
+                }
                 spin_unlock_irqrestore(fence->lock, flags);
         }
 
diff --git a/drivers/dma-buf/sync_debug.h b/drivers/dma-buf/sync_debug.h
index 6a2a8e69a7d0..d615a89f774c 100644
--- a/drivers/dma-buf/sync_debug.h
+++ b/drivers/dma-buf/sync_debug.h
@@ -14,6 +14,7 @@
 #define _LINUX_SYNC_H
 
 #include <linux/list.h>
+#include <linux/rbtree.h>
 #include <linux/spinlock.h>
 #include <linux/dma-fence.h>
 
@@ -25,6 +26,7 @@
  * @kref:               reference count on fence.
  * @name:               name of the sync_timeline. Useful for debugging
  * @lock:               lock protecting @pt_list and @value
+ * @pt_tree:            rbtree of active (unsignaled/errored) sync_pts
  * @pt_list:            list of active (unsignaled/errored) sync_pts
  * @sync_timeline_list: membership in global sync_timeline_list
  */
@@ -36,6 +38,7 @@ struct sync_timeline {
         u64                     context;
         int                     value;
 
+        struct rb_root          pt_tree;
         struct list_head        pt_list;
         spinlock_t              lock;
 
@@ -51,10 +54,12 @@ static inline struct sync_timeline *dma_fence_parent(struct dma_fence *fence)
  * struct sync_pt - sync_pt object
  * @base: base fence object
  * @link: link on the sync timeline's list
+ * @node: node in the sync timeline's tree
  */
 struct sync_pt {
         struct dma_fence base;
         struct list_head link;
+        struct rb_node node;
 };
 
 #ifdef CONFIG_SW_SYNC