1 files changed, 56 insertions, 45 deletions

diff --git a/lib/llist.c b/lib/llist.c
index 4a70d120138c..f574c17a238e 100644
--- a/lib/llist.c
+++ b/lib/llist.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Lock-less NULL terminated single linked list
  *
@@ -8,47 +9,11 @@
  *
  * Copyright 2010,2011 Intel Corp.
  *   Author: Huang Ying <ying.huang@intel.com>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License version
- * 2 as published by the Free Software Foundation;
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 #include <linux/kernel.h>
 #include <linux/export.h>
-#include <linux/interrupt.h>
 #include <linux/llist.h>
 
-
-/**
- * llist_add_batch - add several linked entries in batch
- * @new_first:	first entry in batch to be added
- * @new_last:	last entry in batch to be added
- * @head:	the head for your lock-less list
- *
- * Return whether list is empty before adding.
- */
-bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
-		     struct llist_head *head)
-{
-	struct llist_node *first;
-
-	do {
-		new_last->next = first = ACCESS_ONCE(head->first);
-	} while (cmpxchg(&head->first, first, new_first) != first);
-
-	return !first;
-}
-EXPORT_SYMBOL_GPL(llist_add_batch);
-
 /**
  * llist_del_first - delete the first entry of lock-less list
  * @head:	the head for your lock-less list
@@ -65,19 +30,65 @@ EXPORT_SYMBOL_GPL(llist_add_batch);
  */
 struct llist_node *llist_del_first(struct llist_head *head)
 {
-	struct llist_node *entry, *old_entry, *next;
+	struct llist_node *entry, *next;
 
-	entry = head->first;
-	for (;;) {
+	entry = smp_load_acquire(&head->first);
+	do {
 		if (entry == NULL)
 			return NULL;
-		old_entry = entry;
-		next = entry->next;
-		entry = cmpxchg(&head->first, old_entry, next);
-		if (entry == old_entry)
-			break;
-	}
+		next = READ_ONCE(entry->next);
+	} while (!try_cmpxchg(&head->first, &entry, next));
 
 	return entry;
 }
 EXPORT_SYMBOL_GPL(llist_del_first);
+
+/**
+ * llist_del_first_this - delete given entry of lock-less list if it is first
+ * @head:	the head for your lock-less list
+ * @this:	a list entry.
+ *
+ * If head of the list is given entry, delete and return %true else
+ * return %false.
+ *
+ * Multiple callers can safely call this concurrently with multiple
+ * llist_add() callers, providing all the callers offer a different @this.
+ */
+bool llist_del_first_this(struct llist_head *head,
+			  struct llist_node *this)
+{
+	struct llist_node *entry, *next;
+
+	/* acquire ensures orderig wrt try_cmpxchg() is llist_del_first() */
+	entry = smp_load_acquire(&head->first);
+	do {
+		if (entry != this)
+			return false;
+		next = READ_ONCE(entry->next);
+	} while (!try_cmpxchg(&head->first, &entry, next));
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(llist_del_first_this);
+
+/**
+ * llist_reverse_order - reverse order of a llist chain
+ * @head:	first item of the list to be reversed
+ *
+ * Reverse the order of a chain of llist entries and return the
+ * new first entry.
+ */
+struct llist_node *llist_reverse_order(struct llist_node *head)
+{
+	struct llist_node *new_head = NULL;
+
+	while (head) {
+		struct llist_node *tmp = head;
+		head = head->next;
+		tmp->next = new_head;
+		new_head = tmp;
+	}
+
+	return new_head;
+}
+EXPORT_SYMBOL_GPL(llist_reverse_order);