On Fri, Sep 17, 2021 at 03:27:55PM +0200, Daniel Vetter wrote:

On Fri, Sep 17, 2021 at 02:34:49PM +0200, Christian König wrote:

quoted

A simpler version of the iterator to be used when the dma_resv object is
locked.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 33 +++++++++++++++++++++++++++++++++
 include/linux/dma-resv.h   | 17 +++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 3e77cad2c9d4..a3c79a99fb44 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c

@@ -384,6 +384,39 @@ struct dma_fence *dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor,
 }
 EXPORT_SYMBOL_GPL(dma_resv_iter_walk_unlocked);
 
+/**
+ * dma_resv_iter_walk - walk over fences in a dma_resv obj
+ * @cursor: cursor to record the current position
+ * @first: if we should start over
+ *
+ * Return all the fences in the dma_resv object while holding the
+ * dma_resv::lock.

I think we should document here that the fence is valid for as long as the
dma_resv_lock is held, which is not like the _unlocked version, where the
fence stops being valid either on the next call to iter_next() or on the
call to iter_end() to clean up everything.

Might be good to clarify that also for the unlocked version to be really
precise here when the fence is valid and when not.
-Daniel

quoted

+ */
+struct dma_fence *dma_resv_iter_walk(struct dma_resv_iter *cursor, bool first)
+{
+	dma_resv_assert_held(cursor->obj);
+
+	cursor->is_first = first;
+	if (first) {
+		struct dma_fence *fence;
+
+		cursor->index = -1;
+		cursor->fences = dma_resv_shared_list(cursor->obj);
+
+		fence = dma_resv_excl_fence(cursor->obj);
+		if (fence)
+			return fence;
+	}

I think you can still use the shared iter_begin/end functions even with my
suggestions for patch 1, but would mean changes here too.

quoted

+
+	if (!cursor->all_fences || !cursor->fences ||
+	    ++cursor->index >= cursor->fences->shared_count)
+		return NULL;
+
+	return rcu_dereference_protected(cursor->fences->shared[cursor->index],
+					 dma_resv_held(cursor->obj));
+}
+EXPORT_SYMBOL_GPL(dma_resv_iter_walk);
+
 /**
  * dma_resv_copy_fences - Copy all fences from src to dst.
  * @dst: the destination reservation object

diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index 693d16117153..8c968f8c9d33 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h

@@ -179,6 +179,7 @@ struct dma_resv_iter {
 
 struct dma_fence *dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor,
 					      bool first);
+struct dma_fence *dma_resv_iter_walk(struct dma_resv_iter *cursor, bool first);
 
 /**
  * dma_resv_iter_begin - initialize a dma_resv_iter object

@@ -233,6 +234,22 @@ static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor)
 	for (fence = dma_resv_iter_walk_unlocked(cursor, true);		\
 	     fence; fence = dma_resv_iter_walk_unlocked(cursor, false))
 
+/**
+ * dma_resv_for_each_fence - fence iterator
+ * @cursor: a struct dma_resv_iter pointer
+ * @obj: a dma_resv object pointer
+ * @all_fences: true if all fences should be returned
+ * @fence: the current fence
+ *
+ * Iterate over the fences in a struct dma_resv object while holding the
+ * dma_resv::lock. @all_fences controls if the shared fences are returned as

&dma_resv.lock is how you reference struct members in kerneldoc. I think
you had this also in patch 1.

quoted

+ * well. The cursor initialisation is part of the iterator.

Please also link to the iter_begin/end functions here.

Aside from doc nits and obviously changes due to changes in patch 1 (if we
do them), this looks good.
-Daniel

quoted

+ */
+#define dma_resv_for_each_fence(cursor, obj, all_fences, fence)	\
+	for (dma_resv_iter_begin(cursor, obj, all_fences),	\
+	     fence = dma_resv_iter_walk(cursor, true); fence;	\
+	     fence = dma_resv_iter_walk(cursor, false))
+
 #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
 #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)
 
-- 
2.25.1

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch