winesync: Introduce alertable waits.

Signed-off-by: Alexandre Frade <kernel@xanmod.org>

drivers/misc/winesync.c

@@ -841,10 +841,11 @@ static int setup_wait(struct winesync_device *dev,
 	const __u32 count = args->count;
 	struct winesync_q *q;
 	ktime_t timeout = 0;
+	__u32 total_count;
 	__u32 *ids;
 	__u32 i, j;
 
-	if (!args->owner || args->pad)
+	if (!args->owner)
 		return -EINVAL;
 
 	if (args->timeout) {
@@ -858,16 +859,22 @@ static int setup_wait(struct winesync_device *dev,
 		timeout = timespec64_to_ns(&to);
 	}
 
-	ids = kmalloc_array(count, sizeof(*ids), GFP_KERNEL);
+	total_count = count;
+	if (args->alert)
+		total_count++;
+
+	ids = kmalloc_array(total_count, sizeof(*ids), GFP_KERNEL);
 	if (!ids)
 		return -ENOMEM;
 	if (copy_from_user(ids, u64_to_user_ptr(args->objs),
 			   array_size(count, sizeof(*ids)))) {
 		kfree(ids);
 		return -EFAULT;
 	}
+	if (args->alert)
+		ids[count] = args->alert;
 
-	q = kmalloc(struct_size(q, entries, count), GFP_KERNEL);
+	q = kmalloc(struct_size(q, entries, total_count), GFP_KERNEL);
 	if (!q) {
 		kfree(ids);
 		return -ENOMEM;
@@ -879,7 +886,7 @@ static int setup_wait(struct winesync_device *dev,
 	q->ownerdead = false;
 	q->count = count;
 
-	for (i = 0; i < count; i++) {
+	for (i = 0; i < total_count; i++) {
 		struct winesync_q_entry *entry = &q->entries[i];
 		struct winesync_obj *obj = get_obj(dev, ids[i]);
 
@@ -934,9 +941,9 @@ static int winesync_wait_any(struct winesync_device *dev, void __user *argp)
 {
 	struct winesync_wait_args args;
 	struct winesync_q *q;
+	__u32 i, total_count;
 	ktime_t timeout;
 	int signaled;
-	__u32 i;
 	int ret;
 
 	if (copy_from_user(&args, argp, sizeof(args)))
@@ -946,9 +953,13 @@ static int winesync_wait_any(struct winesync_device *dev, void __user *argp)
 	if (ret < 0)
 		return ret;
 
+	total_count = args.count;
+	if (args.alert)
+		total_count++;
+
 	/* queue ourselves */
 
-	for (i = 0; i < args.count; i++) {
+	for (i = 0; i < total_count; i++) {
 		struct winesync_q_entry *entry = &q->entries[i];
 		struct winesync_obj *obj = entry->obj;
 
@@ -957,9 +968,15 @@ static int winesync_wait_any(struct winesync_device *dev, void __user *argp)
 		spin_unlock(&obj->lock);
 	}
 
-	/* check if we are already signaled */
+	/*
+	 * Check if we are already signaled.
+	 *
+	 * Note that the API requires that normal objects are checked before
+	 * the alert event. Hence we queue the alert event last, and check
+	 * objects in order.
+	 */
 
-	for (i = 0; i < args.count; i++) {
+	for (i = 0; i < total_count; i++) {
 		struct winesync_obj *obj = q->entries[i].obj;
 
 		if (atomic_read(&q->signaled) != -1)
@@ -976,7 +993,7 @@ static int winesync_wait_any(struct winesync_device *dev, void __user *argp)
 
 	/* and finally, unqueue */
 
-	for (i = 0; i < args.count; i++) {
+	for (i = 0; i < total_count; i++) {
 		struct winesync_q_entry *entry = &q->entries[i];
 		struct winesync_obj *obj = entry->obj;
 
@@ -1036,13 +1053,36 @@ static int winesync_wait_all(struct winesync_device *dev, void __user *argp)
 		 */
 		list_add_tail(&entry->node, &obj->all_waiters);
 	}
+	if (args.alert) {
+		struct winesync_q_entry *entry = &q->entries[args.count];
+		struct winesync_obj *obj = entry->obj;
+
+		spin_lock(&obj->lock);
+		list_add_tail(&entry->node, &obj->any_waiters);
+		spin_unlock(&obj->lock);
+	}
 
 	/* check if we are already signaled */
 
 	try_wake_all(dev, q, NULL);
 
 	spin_unlock(&dev->wait_all_lock);
 
+	/*
+	 * Check if the alert event is signaled, making sure to do so only
+	 * after checking if the other objects are signaled.
+	 */
+
+	if (args.alert) {
+		struct winesync_obj *obj = q->entries[args.count].obj;
+
+		if (atomic_read(&q->signaled) == -1) {
+			spin_lock(&obj->lock);
+			try_wake_any_obj(obj);
+			spin_unlock(&obj->lock);
+		}
+	}
+
 	/* sleep */
 
 	ret = winesync_schedule(q, args.timeout ? &timeout : NULL);
@@ -1065,6 +1105,16 @@ static int winesync_wait_all(struct winesync_device *dev, void __user *argp)
 
 		put_obj(obj);
 	}
+	if (args.alert) {
+		struct winesync_q_entry *entry = &q->entries[args.count];
+		struct winesync_obj *obj = entry->obj;
+
+		spin_lock(&obj->lock);
+		list_del(&entry->node);
+		spin_unlock(&obj->lock);
+
+		put_obj(obj);
+	}
 
 	spin_unlock(&dev->wait_all_lock);
 

include/uapi/linux/winesync.h

@@ -34,7 +34,7 @@ struct winesync_wait_args {
 	__u32 count;
 	__u32 owner;
 	__u32 index;
-	__u32 pad;
+	__u32 alert;
 };
 
 #define WINESYNC_IOC_BASE 0xf7