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authorChristian König <christian.koenig@amd.com>2021-06-15 16:10:03 +0300
committerChristian König <christian.koenig@amd.com>2021-10-06 10:48:01 +0300
commitc921ff373b469ad7907cde219fa700909f59cac4 (patch)
treeecb4e8ff3e0f15356853153cef2fa406920ffb03 /include/linux/dma-resv.h
parente7bd95a7ed4e4c8aa82a33f89eb09f596cf37a4b (diff)
downloadlinux-c921ff373b469ad7907cde219fa700909f59cac4.tar.xz
dma-buf: add dma_resv_for_each_fence_unlocked v8
Abstract the complexity of iterating over all the fences in a dma_resv object. The new loop handles the whole RCU and retry dance and returns only fences where we can be sure we grabbed the right one. v2: fix accessing the shared fences while they might be freed, improve kerneldoc, rename _cursor to _iter, add dma_resv_iter_is_exclusive, add dma_resv_iter_begin/end v3: restructor the code, move rcu_read_lock()/unlock() into the iterator, add dma_resv_iter_is_restarted() v4: fix NULL deref when no explicit fence exists, drop superflous rcu_read_lock()/unlock() calls. v5: fix typos in the documentation v6: fix coding error when excl fence is NULL v7: one more logic fix v8: fix index check in dma_resv_iter_is_exclusive() Signed-off-by: Christian König <christian.koenig@amd.com> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> (v7) Link: https://patchwork.freedesktop.org/patch/msgid/20211005113742.1101-2-christian.koenig@amd.com
Diffstat (limited to 'include/linux/dma-resv.h')
-rw-r--r--include/linux/dma-resv.h95
1 files changed, 95 insertions, 0 deletions
diff --git a/include/linux/dma-resv.h b/include/linux/dma-resv.h
index 9100dd3dc21f..764138ad8583 100644
--- a/include/linux/dma-resv.h
+++ b/include/linux/dma-resv.h
@@ -149,6 +149,101 @@ struct dma_resv {
struct dma_resv_list __rcu *fence;
};
+/**
+ * struct dma_resv_iter - current position into the dma_resv fences
+ *
+ * Don't touch this directly in the driver, use the accessor function instead.
+ */
+struct dma_resv_iter {
+ /** @obj: The dma_resv object we iterate over */
+ struct dma_resv *obj;
+
+ /** @all_fences: If all fences should be returned */
+ bool all_fences;
+
+ /** @fence: the currently handled fence */
+ struct dma_fence *fence;
+
+ /** @seq: sequence number to check for modifications */
+ unsigned int seq;
+
+ /** @index: index into the shared fences */
+ unsigned int index;
+
+ /** @fences: the shared fences */
+ struct dma_resv_list *fences;
+
+ /** @is_restarted: true if this is the first returned fence */
+ bool is_restarted;
+};
+
+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);
+
+/**
+ * dma_resv_iter_begin - initialize a dma_resv_iter object
+ * @cursor: The dma_resv_iter object to initialize
+ * @obj: The dma_resv object which we want to iterate over
+ * @all_fences: If all fences should be returned or just the exclusive one
+ */
+static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
+ struct dma_resv *obj,
+ bool all_fences)
+{
+ cursor->obj = obj;
+ cursor->all_fences = all_fences;
+ cursor->fence = NULL;
+}
+
+/**
+ * dma_resv_iter_end - cleanup a dma_resv_iter object
+ * @cursor: the dma_resv_iter object which should be cleaned up
+ *
+ * Make sure that the reference to the fence in the cursor is properly
+ * dropped.
+ */
+static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
+{
+ dma_fence_put(cursor->fence);
+}
+
+/**
+ * dma_resv_iter_is_exclusive - test if the current fence is the exclusive one
+ * @cursor: the cursor of the current position
+ *
+ * Returns true if the currently returned fence is the exclusive one.
+ */
+static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor)
+{
+ return cursor->index == 0;
+}
+
+/**
+ * dma_resv_iter_is_restarted - test if this is the first fence after a restart
+ * @cursor: the cursor with the current position
+ *
+ * Return true if this is the first fence in an iteration after a restart.
+ */
+static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
+{
+ return cursor->is_restarted;
+}
+
+/**
+ * dma_resv_for_each_fence_unlocked - unlocked fence iterator
+ * @cursor: a struct dma_resv_iter pointer
+ * @fence: the current fence
+ *
+ * Iterate over the fences in a struct dma_resv object without holding the
+ * &dma_resv.lock and using RCU instead. The cursor needs to be initialized
+ * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside
+ * the iterator a reference to the dma_fence is held and the RCU lock dropped.
+ * When the dma_resv is modified the iteration starts over again.
+ */
+#define dma_resv_for_each_fence_unlocked(cursor, fence) \
+ for (fence = dma_resv_iter_first_unlocked(cursor); \
+ fence; fence = dma_resv_iter_next_unlocked(cursor))
+
#define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base)
#define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base)