kernel

linux-6.8.1/include/linux/rculist_bl.h

@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_RCULIST_BL_H
+#define _LINUX_RCULIST_BL_H
+
+/*
+ * RCU-protected bl list version. See include/linux/list_bl.h.
+ */
+#include <linux/list_bl.h>
+#include <linux/rcupdate.h>
+
+static inline void hlist_bl_set_first_rcu(struct hlist_bl_head *h,
+					struct hlist_bl_node *n)
+{
+	LIST_BL_BUG_ON((unsigned long)n & LIST_BL_LOCKMASK);
+	LIST_BL_BUG_ON(((unsigned long)h->first & LIST_BL_LOCKMASK) !=
+							LIST_BL_LOCKMASK);
+	rcu_assign_pointer(h->first,
+		(struct hlist_bl_node *)((unsigned long)n | LIST_BL_LOCKMASK));
+}
+
+static inline struct hlist_bl_node *hlist_bl_first_rcu(struct hlist_bl_head *h)
+{
+	return (struct hlist_bl_node *)
+		((unsigned long)rcu_dereference_check(h->first, hlist_bl_is_locked(h)) & ~LIST_BL_LOCKMASK);
+}
+
+/**
+ * hlist_bl_del_rcu - deletes entry from hash list without re-initialization
+ * @n: the element to delete from the hash list.
+ *
+ * Note: hlist_bl_unhashed() on entry does not return true after this,
+ * the entry is in an undefined state. It is useful for RCU based
+ * lockfree traversal.
+ *
+ * In particular, it means that we can not poison the forward
+ * pointers that may still be used for walking the hash list.
+ *
+ * The caller must take whatever precautions are necessary
+ * (such as holding appropriate locks) to avoid racing
+ * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
+ * or hlist_bl_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_bl_for_each_entry().
+ */
+static inline void hlist_bl_del_rcu(struct hlist_bl_node *n)
+{
+	__hlist_bl_del(n);
+	n->pprev = LIST_POISON2;
+}
+
+/**
+ * hlist_bl_add_head_rcu
+ * @n: the element to add to the hash list.
+ * @h: the list to add to.
+ *
+ * Description:
+ * Adds the specified element to the specified hlist_bl,
+ * while permitting racing traversals.
+ *
+ * The caller must take whatever precautions are necessary
+ * (such as holding appropriate locks) to avoid racing
+ * with another list-mutation primitive, such as hlist_bl_add_head_rcu()
+ * or hlist_bl_del_rcu(), running on this same list.
+ * However, it is perfectly legal to run concurrently with
+ * the _rcu list-traversal primitives, such as
+ * hlist_bl_for_each_entry_rcu(), used to prevent memory-consistency
+ * problems on Alpha CPUs.  Regardless of the type of CPU, the
+ * list-traversal primitive must be guarded by rcu_read_lock().
+ */
+static inline void hlist_bl_add_head_rcu(struct hlist_bl_node *n,
+					struct hlist_bl_head *h)
+{
+	struct hlist_bl_node *first;
+
+	/* don't need hlist_bl_first_rcu because we're under lock */
+	first = hlist_bl_first(h);
+
+	n->next = first;
+	if (first)
+		first->pprev = &n->next;
+	n->pprev = &h->first;
+
+	/* need _rcu because we can have concurrent lock free readers */
+	hlist_bl_set_first_rcu(h, n);
+}
+/**
+ * hlist_bl_for_each_entry_rcu - iterate over rcu list of given type
+ * @tpos:	the type * to use as a loop cursor.
+ * @pos:	the &struct hlist_bl_node to use as a loop cursor.
+ * @head:	the head for your list.
+ * @member:	the name of the hlist_bl_node within the struct.
+ *
+ */
+#define hlist_bl_for_each_entry_rcu(tpos, pos, head, member)		\
+	for (pos = hlist_bl_first_rcu(head);				\
+		pos &&							\
+		({ tpos = hlist_bl_entry(pos, typeof(*tpos), member); 1; }); \
+		pos = rcu_dereference_raw(pos->next))
+
+#endif