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-rw-r--r--lib/llist.c129
1 files changed, 129 insertions, 0 deletions
diff --git a/lib/llist.c b/lib/llist.c
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+++ b/lib/llist.c
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+/*
+ * 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 handler. So code uses the list in NMI
+ * handler should depend on CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG.
+ *
+ * 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/module.h>
+#include <linux/interrupt.h>
+#include <linux/llist.h>
+
+#include <asm/system.h>
+
+/**
+ * llist_add - add a new entry
+ * @new: new entry to be added
+ * @head: the head for your lock-less list
+ */
+void llist_add(struct llist_node *new, 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 {
+ old_entry = entry;
+ new->next = entry;
+ cpu_relax();
+ } while ((entry = cmpxchg(&head->first, old_entry, new)) != old_entry);
+}
+EXPORT_SYMBOL_GPL(llist_add);
+
+/**
+ * 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
+ */
+void 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 {
+ old_entry = entry;
+ new_last->next = entry;
+ cpu_relax();
+ } while ((entry = cmpxchg(&head->first, old_entry, new_first)) != old_entry);
+}
+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;
+
+#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
+ BUG_ON(in_nmi());
+#endif
+
+ entry = head->first;
+ do {
+ if (entry == NULL)
+ return NULL;
+ old_entry = entry;
+ next = entry->next;
+ cpu_relax();
+ } while ((entry = cmpxchg(&head->first, old_entry, next)) != old_entry);
+
+ return entry;
+}
+EXPORT_SYMBOL_GPL(llist_del_first);
+
+/**
+ * llist_del_all - delete all entries from lock-less list
+ * @head: the head of lock-less list to delete all entries
+ *
+ * If list is empty, return NULL, otherwise, delete all entries and
+ * return the pointer to the first entry. The order of entries
+ * deleted is from the newest to the oldest added one.
+ */
+struct llist_node *llist_del_all(struct llist_head *head)
+{
+#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
+ BUG_ON(in_nmi());
+#endif
+
+ return xchg(&head->first, NULL);
+}
+EXPORT_SYMBOL_GPL(llist_del_all);

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