dma-buf/dma-fence: Add dma_fence_test_signaled_flag()

The dma_fence framework checks at many places whether the signaled flag
of a fence is already set. The code can be simplified and made more
readable by providing a helper function for that.

Add dma_fence_test_signaled_flag(), which only checks whether a fence is
signaled. Use it internally.

Suggested-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Philipp Stanner <phasta@kernel.org>
Link: https://patch.msgid.link/20251201105011.19386-3-phasta@kernel.org

2 files changed, 30 insertions, 10 deletions

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 2bb18af369b9..5e96cb5f1f3b 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -543,7 +543,7 @@ void dma_fence_release(struct kref *kref)
 	trace_dma_fence_destroy(fence);
 
 	if (!list_empty(&fence->cb_list) &&
-	    !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+	    !dma_fence_test_signaled_flag(fence)) {
 		const char __rcu *timeline;
 		const char __rcu *driver;
 		unsigned long flags;
@@ -600,7 +600,7 @@ static bool __dma_fence_enable_signaling(struct dma_fence *fence)
 	was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
 				   &fence->flags);
 
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (dma_fence_test_signaled_flag(fence))
 		return false;
 
 	if (!was_set && fence->ops->enable_signaling) {
@@ -664,7 +664,7 @@ int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
 	if (WARN_ON(!fence || !func))
 		return -EINVAL;
 
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+	if (dma_fence_test_signaled_flag(fence)) {
 		INIT_LIST_HEAD(&cb->node);
 		return -ENOENT;
 	}
@@ -781,7 +781,7 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
 
 	spin_lock_irqsave(fence->lock, flags);
 
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (dma_fence_test_signaled_flag(fence))
 		goto out;
 
 	if (intr && signal_pending(current)) {
@@ -798,7 +798,7 @@ dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
 	cb.task = current;
 	list_add(&cb.base.node, &fence->cb_list);
 
-	while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
+	while (!dma_fence_test_signaled_flag(fence) && ret > 0) {
 		if (intr)
 			__set_current_state(TASK_INTERRUPTIBLE);
 		else
@@ -830,7 +830,7 @@ dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
 
 	for (i = 0; i < count; ++i) {
 		struct dma_fence *fence = fences[i];
-		if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
+		if (dma_fence_test_signaled_flag(fence)) {
 			if (idx)
 				*idx = i;
 			return true;
@@ -1108,7 +1108,7 @@ const char __rcu *dma_fence_driver_name(struct dma_fence *fence)
 	RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
 			 "RCU protection is required for safe access to returned string");
 
-	if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (!dma_fence_test_signaled_flag(fence))
 		return fence->ops->get_driver_name(fence);
 	else
 		return "detached-driver";
@@ -1140,7 +1140,7 @@ const char __rcu *dma_fence_timeline_name(struct dma_fence *fence)
 	RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
 			 "RCU protection is required for safe access to returned string");
 
-	if (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (!dma_fence_test_signaled_flag(fence))
 		return fence->ops->get_driver_name(fence);
 	else
 		return "signaled-timeline";
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 64639e104110..19972f5d176f 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -401,6 +401,26 @@ void dma_fence_enable_sw_signaling(struct dma_fence *fence);
 const char __rcu *dma_fence_driver_name(struct dma_fence *fence);
 const char __rcu *dma_fence_timeline_name(struct dma_fence *fence);
 
+/*
+ * dma_fence_test_signaled_flag - Only check whether a fence is signaled yet.
+ * @fence: the fence to check
+ *
+ * This function just checks whether @fence is signaled, without interacting
+ * with the fence in any way. The user must, therefore, ensure through other
+ * means that fences get signaled eventually.
+ *
+ * This function uses test_bit(), which is thread-safe. Naturally, this function
+ * should be used opportunistically; a fence could get signaled at any moment
+ * after the check is done.
+ *
+ * Return: true if signaled, false otherwise.
+ */
+static inline bool
+dma_fence_test_signaled_flag(struct dma_fence *fence)
+{
+	return test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags);
+}
+
 /**
  * dma_fence_is_signaled_locked - Return an indication if the fence
  *                                is signaled yet.
@@ -418,7 +438,7 @@ const char __rcu *dma_fence_timeline_name(struct dma_fence *fence);
 static inline bool
 dma_fence_is_signaled_locked(struct dma_fence *fence)
 {
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (dma_fence_test_signaled_flag(fence))
 		return true;
 
 	if (fence->ops->signaled && fence->ops->signaled(fence)) {
@@ -448,7 +468,7 @@ dma_fence_is_signaled_locked(struct dma_fence *fence)
 static inline bool
 dma_fence_is_signaled(struct dma_fence *fence)
 {
-	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+	if (dma_fence_test_signaled_flag(fence))
 		return true;
 
 	if (fence->ops->signaled && fence->ops->signaled(fence)) {