Move c_src dirs back to toplevel

[bcachefs-tools-debian] / linux / llist.c

diff --git a/linux/llist.c b/linux/llist.c
new file mode 100644 (file)
index 0000000..611ce48
--- /dev/null
+++ b/linux/llist.c
@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Lock-less NULL terminated single linked list
+ *
+ * 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 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>
+ */
+#include <linux/kernel.h>
+#include <linux/export.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 = READ_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
+ *
+ * If list is empty, return NULL, otherwise, return the first entry
+ * deleted, this is the newest added one.
+ *
+ * Only one llist_del_first user can be used simultaneously with
+ * multiple llist_add users without lock.  Because otherwise
+ * llist_del_first, llist_add, llist_add (or llist_del_all, llist_add,
+ * llist_add) sequence in another user may change @head->first->next,
+ * but keep @head->first.  If multiple consumers are needed, please
+ * use llist_del_all or use lock between consumers.
+ */
+struct llist_node *llist_del_first(struct llist_head *head)
+{
+       struct llist_node *entry, *old_entry, *next;
+
+       entry = smp_load_acquire(&head->first);
+       for (;;) {
+               if (entry == NULL)
+                       return NULL;
+               old_entry = entry;
+               next = READ_ONCE(entry->next);
+               entry = cmpxchg(&head->first, old_entry, next);
+               if (entry == old_entry)
+                       break;
+       }
+
+       return entry;
+}
+EXPORT_SYMBOL_GPL(llist_del_first);
+
+/**
+ * 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);