*
* The basic atomic operation of this list is cmpxchg on long. On
* architectures that don't have NMI-safe cmpxchg implementation, the
- * list can NOT be used in NMI handler. So code uses the list in NMI
- * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
+ * list can NOT be used in NMI handlers. So code that uses the list in
+ * an NMI handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
*
* Copyright 2010,2011 Intel Corp.
* Author: Huang Ying <ying.huang@intel.com>
* @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.
*/
-void llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
+bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
struct llist_head *head)
{
struct llist_node *entry, *old_entry;
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
- BUG_ON(in_nmi());
-#endif
-
entry = head->first;
- do {
+ for (;;) {
old_entry = entry;
new_last->next = entry;
- cpu_relax();
- } while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
+ entry = cmpxchg(&head->first, old_entry, new_first);
+ if (entry == old_entry)
+ break;
+ }
+
+ return old_entry == NULL;
}
EXPORT_SYMBOL_GPL(llist_add_batch);
{
struct llist_node *entry, *old_entry, *next;
-#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
- BUG_ON(in_nmi());
-#endif
-
entry = head->first;
- do {
+ for (;;) {
if (entry == NULL)
return NULL;
old_entry = entry;
next = entry->next;
- cpu_relax();
- } while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
+ entry = cmpxchg(&head->first, old_entry, next);
+ if (entry == old_entry)
+ break;
+ }
return entry;
}