All of lore.kernel.org
 help / color / mirror / Atom feed
* [Intel-gfx] [PATCH 01/25] dma-buf: add dma_resv_for_each_fence_unlocked v5
@ 2021-09-23  7:55 Christian König
  2021-09-23  7:55 ` [Intel-gfx] [PATCH 02/25] dma-buf: add dma_resv_for_each_fence Christian König
                   ` (26 more replies)
  0 siblings, 27 replies; 32+ messages in thread
From: Christian König @ 2021-09-23  7:55 UTC (permalink / raw)
  To: intel-gfx

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

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/dma-buf/dma-resv.c | 95 ++++++++++++++++++++++++++++++++++++++
 include/linux/dma-resv.h   | 95 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 190 insertions(+)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 84fbe60629e3..fbd00e4e1fb4 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -323,6 +323,101 @@ void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence)
 }
 EXPORT_SYMBOL(dma_resv_add_excl_fence);
 
+/**
+ * dma_resv_iter_restart_unlocked - restart the unlocked iterator
+ * @cursor: The dma_resv_iter object to restart
+ *
+ * Restart the unlocked iteration by initializing the cursor object.
+ */
+static void dma_resv_iter_restart_unlocked(struct dma_resv_iter *cursor)
+{
+	cursor->seq = read_seqcount_begin(&cursor->obj->seq);
+	cursor->index = -1;
+	if (cursor->all_fences)
+		cursor->fences = dma_resv_shared_list(cursor->obj);
+	else
+		cursor->fences = NULL;
+	cursor->is_restarted = true;
+}
+
+/**
+ * dma_resv_iter_walk_unlocked - walk over fences in a dma_resv obj
+ * @cursor: cursor to record the current position
+ *
+ * Return all the fences in the dma_resv object which are not yet signaled.
+ * The returned fence has an extra local reference so will stay alive.
+ * If a concurrent modify is detected the whole iteration is started over again.
+ */
+static void dma_resv_iter_walk_unlocked(struct dma_resv_iter *cursor)
+{
+	struct dma_resv *obj = cursor->obj;
+
+	do {
+		/* Drop the reference from the previous round */
+		dma_fence_put(cursor->fence);
+
+		if (cursor->index++ == -1) {
+			cursor->fence = dma_resv_excl_fence(obj);
+
+		} else if (!cursor->fences ||
+			   cursor->index >= cursor->fences->shared_count) {
+			cursor->fence = NULL;
+
+		} else {
+			struct dma_resv_list *fences = cursor->fences;
+			unsigned int idx = cursor->index;
+
+			cursor->fence = rcu_dereference(fences->shared[idx]);
+		}
+		if (cursor->fence)
+			cursor->fence = dma_fence_get_rcu(cursor->fence);
+	} while (cursor->fence && dma_fence_is_signaled(cursor->fence));
+}
+
+/**
+ * dma_resv_iter_first_unlocked - first fence in an unlocked dma_resv obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the first fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor)
+{
+	rcu_read_lock();
+	do {
+		dma_resv_iter_restart_unlocked(cursor);
+		dma_resv_iter_walk_unlocked(cursor);
+	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+	rcu_read_unlock();
+
+	return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_first_unlocked);
+
+/**
+ * dma_resv_iter_next_unlocked - next fence in an unlocked dma_resv obj.
+ * @cursor: the cursor with the current position
+ *
+ * Returns the next fence from an unlocked dma_resv obj.
+ */
+struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor)
+{
+	bool restart;
+
+	rcu_read_lock();
+	cursor->is_restarted = false;
+	restart = read_seqcount_retry(&cursor->obj->seq, cursor->seq);
+	do {
+		if (restart)
+			dma_resv_iter_restart_unlocked(cursor);
+		dma_resv_iter_walk_unlocked(cursor);
+		restart = true;
+	} while (read_seqcount_retry(&cursor->obj->seq, cursor->seq));
+	rcu_read_unlock();
+
+	return cursor->fence;
+}
+EXPORT_SYMBOL(dma_resv_iter_next_unlocked);
+
 /**
  * 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 9100dd3dc21f..5d7d28cb9008 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 == -1;
+}
+
+/**
+ * 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)
 
-- 
2.25.1


^ permalink raw reply related	[flat|nested] 32+ messages in thread
end of thread, other threads:[~2021-09-24 12:32 UTC | newest]

Thread overview: 32+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-23  7:55 [Intel-gfx] [PATCH 01/25] dma-buf: add dma_resv_for_each_fence_unlocked v5 Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 02/25] dma-buf: add dma_resv_for_each_fence Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 03/25] dma-buf: use new iterator in dma_resv_copy_fences Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 04/25] dma-buf: use new iterator in dma_resv_get_fences v3 Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 05/25] dma-buf: use new iterator in dma_resv_wait_timeout Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 06/25] dma-buf: use new iterator in dma_resv_test_signaled Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 07/25] drm/ttm: use the new iterator in ttm_bo_flush_all_fences Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 08/25] drm/amdgpu: use the new iterator in amdgpu_sync_resv Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 09/25] drm/amdgpu: use new iterator in amdgpu_ttm_bo_eviction_valuable Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 10/25] drm/amdgpu: use new iterator in amdgpu_vm_prt_fini Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 11/25] drm/msm: use new iterator in msm_gem_describe Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 12/25] drm/radeon: use new iterator in radeon_sync_resv Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 13/25] drm/scheduler: use new iterator in drm_sched_job_add_implicit_dependencies v2 Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 14/25] drm/i915: use the new iterator in i915_gem_busy_ioctl v2 Christian König
2021-09-24  9:08   ` Tvrtko Ursulin
2021-09-23  7:55 ` [Intel-gfx] [PATCH 15/25] drm/i915: use the new iterator in i915_sw_fence_await_reservation v3 Christian König
2021-09-23  7:55 ` [Intel-gfx] [PATCH 16/25] drm/i915: use the new iterator in i915_request_await_object v2 Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 17/25] drm/i915: use new iterator in i915_gem_object_wait_reservation Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 18/25] drm/i915: use new iterator in i915_gem_object_wait_priority Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 19/25] drm/i915: use new cursor in intel_prepare_plane_fb Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 20/25] drm: use new iterator in drm_gem_fence_array_add_implicit v3 Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 21/25] drm: use new iterator in drm_gem_plane_helper_prepare_fb Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 22/25] drm/nouveau: use the new iterator in nouveau_fence_sync Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 23/25] drm/nouveau: use the new interator in nv50_wndw_prepare_fb Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 24/25] drm/etnaviv: use new iterator in etnaviv_gem_describe Christian König
2021-09-23  7:56 ` [Intel-gfx] [PATCH 25/25] drm/etnaviv: replace dma_resv_get_excl_unlocked Christian König
2021-09-23 12:32 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for series starting with [01/25] dma-buf: add dma_resv_for_each_fence_unlocked v5 Patchwork
2021-09-23 12:35 ` [Intel-gfx] ✗ Fi.CI.SPARSE: " Patchwork
2021-09-23 13:05 ` [Intel-gfx] ✗ Fi.CI.BAT: failure " Patchwork
2021-09-24  9:11   ` Tvrtko Ursulin
2021-09-24  9:13     ` Christian König
2021-09-24 10:08       ` Tvrtko Ursulin

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.