dma-buf/fence: add fence_wait_any_timeout function v2

Waiting for the first fence in an array of fences to signal.

This is useful for device driver specific resource managers
and also Vulkan needs something similar.

v2: more parameter checks, handling for timeout==0,
    remove NULL entry support, better callback removal.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

drivers/dma-buf/fence.c

@@ -397,6 +397,104 @@ out:
 }
 EXPORT_SYMBOL(fence_default_wait);
 
+static bool
+fence_test_signaled_any(struct fence **fences, uint32_t count)
+{
+	int i;
+
+	for (i = 0; i < count; ++i) {
+		struct fence *fence = fences[i];
+		if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->flags))
+			return true;
+	}
+	return false;
+}
+
+/**
+ * fence_wait_any_timeout - sleep until any fence gets signaled
+ * or until timeout elapses
+ * @fences:	[in]	array of fences to wait on
+ * @count:	[in]	number of fences to wait on
+ * @intr:	[in]	if true, do an interruptible wait
+ * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
+ *
+ * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
+ * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
+ * on success.
+ *
+ * Synchronous waits for the first fence in the array to be signaled. The
+ * caller needs to hold a reference to all fences in the array, otherwise a
+ * fence might be freed before return, resulting in undefined behavior.
+ */
+signed long
+fence_wait_any_timeout(struct fence **fences, uint32_t count,
+		       bool intr, signed long timeout)
+{
+	struct default_wait_cb *cb;
+	signed long ret = timeout;
+	unsigned i;
+
+	if (WARN_ON(!fences || !count || timeout < 0))
+		return -EINVAL;
+
+	if (timeout == 0) {
+		for (i = 0; i < count; ++i)
+			if (fence_is_signaled(fences[i]))
+				return 1;
+
+		return 0;
+	}
+
+	cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
+	if (cb == NULL) {
+		ret = -ENOMEM;
+		goto err_free_cb;
+	}
+
+	for (i = 0; i < count; ++i) {
+		struct fence *fence = fences[i];
+
+		if (fence->ops->wait != fence_default_wait) {
+			ret = -EINVAL;
+			goto fence_rm_cb;
+		}
+
+		cb[i].task = current;
+		if (fence_add_callback(fence, &cb[i].base,
+				       fence_default_wait_cb)) {
+			/* This fence is already signaled */
+			goto fence_rm_cb;
+		}
+	}
+
+	while (ret > 0) {
+		if (intr)
+			set_current_state(TASK_INTERRUPTIBLE);
+		else
+			set_current_state(TASK_UNINTERRUPTIBLE);
+
+		if (fence_test_signaled_any(fences, count))
+			break;
+
+		ret = schedule_timeout(ret);
+
+		if (ret > 0 && intr && signal_pending(current))
+			ret = -ERESTARTSYS;
+	}
+
+	__set_current_state(TASK_RUNNING);
+
+fence_rm_cb:
+	while (i-- > 0)
+		fence_remove_callback(fences[i], &cb[i].base);
+
+err_free_cb:
+	kfree(cb);
+
+	return ret;
+}
+EXPORT_SYMBOL(fence_wait_any_timeout);
+
 /**
  * fence_init - Initialize a custom fence.
  * @fence:	[in]	the fence to initialize

include/linux/fence.h

@@ -305,7 +305,8 @@ static inline struct fence *fence_later(struct fence *f1, struct fence *f2)
 }
 
 signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout);
-
+signed long fence_wait_any_timeout(struct fence **fences, uint32_t count,
+				   bool intr, signed long timeout);
 
 /**
  * fence_wait - sleep until the fence gets signaled