On 06/10/2021 09:40, Tvrtko Ursulin wrote:
On 05/10/2021 12:37, Christian König wrote:
A simpler version of the iterator to be used when the dma_resv object is
locked.
v2: fix index check here as well
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-resv.c | 49 ++++++++++++++++++++++++++++++++++++++
include/linux/dma-resv.h | 19 +++++++++++++++
2 files changed, 68 insertions(+)
diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 3cbcf66a137e..231bae173ef1 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -423,6 +423,55 @@ struct dma_fence
*dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
}
EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
+/**
+ * dma_resv_iter_first - first fence from a locked dma_resv object
+ * @cursor: cursor to record the current position
+ *
+ * Return all the fences in the dma_resv object while holding the
+ * &dma_resv.lock.
+ */
+struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor)
+{
+ struct dma_fence *fence;
+
+ dma_resv_assert_held(cursor->obj);
+
+ cursor->index = 0;
+ cursor->fences = dma_resv_shared_list(cursor->obj);
+
+ fence = dma_resv_excl_fence(cursor->obj);
+ if (!fence)
+ fence = dma_resv_iter_next(cursor);
"Is restarted" probably does not matter hugely for the locked iterator
but I think if it hits this path (no exclusive fence, returns first
shared) then it will show it as false. Which is not consistent with the
unlocked iterator.
Sorry I was blind or I don't know which version of which patch I was
looking at.. It is set to true a few lines below. :)
Regards,
Tvrtko
Bonus points if you make a debug build assert that makes querying "is
restarted" warn when used with the locked iterator.
+
+ cursor->is_restarted = true;
+ return fence;
+}
+EXPORT_SYMBOL_GPL(dma_resv_iter_first);
+
+/**
+ * dma_resv_iter_next - next fence from a locked dma_resv object
+ * @cursor: cursor to record the current position
+ *
+ * Return all the fences in the dma_resv object while holding the
+ * &dma_resv.lock.
You probably want to replace "all the fences" with first and next,
respectively, in here and in dma_resv_iter_first kerneldoc.
+ */
+struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor)
+{
+ unsigned int idx;
+
+ dma_resv_assert_held(cursor->obj);
+
+ cursor->is_restarted = false;
+ if (!cursor->all_fences || !cursor->fences ||
+ cursor->index >= cursor->fences->shared_count)
+ return NULL;
Theoretically you could store the shared count in the cursor and so
could have a single condition here (assuming initialized to zero when
!all_fences and !cursor->fences). For some value of optimisation. :)
Probably not worth it.
But you could only assign cursor->fences if all_fences, in
dma_resv_iter_first, so wouldn't have to duplicate the all_fences check
here.
+
+ idx = cursor->index++;
+ return rcu_dereference_protected(cursor->fences->shared[idx],
+ dma_resv_held(cursor->obj));
+}
+EXPORT_SYMBOL_GPL(dma_resv_iter_next);
+
/**
* 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 764138ad8583..3df7ef23712d 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -179,6 +179,8 @@ struct dma_resv_iter {
struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter
*cursor);
struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter
*cursor);
+struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor);
+struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor);
/**
* dma_resv_iter_begin - initialize a dma_resv_iter object
@@ -244,6 +246,23 @@ static inline bool
dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
for (fence = dma_resv_iter_first_unlocked(cursor); \
fence; fence = dma_resv_iter_next_unlocked(cursor))
+/**
+ * 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
+ * well. The cursor initialisation is part of the iterator and the
fence stays
+ * valid as long as the lock is held.
I'd be super cautious and explicitly spell out that reference is not
held in contrast to the unlocked iterator.
+ */
+#define dma_resv_for_each_fence(cursor, obj, all_fences, fence) \
+ for (dma_resv_iter_begin(cursor, obj, all_fences), \
+ fence = dma_resv_iter_first(cursor); fence; \
+ fence = dma_resv_iter_next(cursor))
+
#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
#define dma_resv_assert_held(obj)
lockdep_assert_held(&(obj)->lock.base)
Regards,
Tvrtko
