add hash, plist, etc (untested)

c/plist.c

@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * adapted from Linux kernel lib/plist.c
+ *
+ * Descending-priority-sorted double-linked list
+ *
+ * (C) 2002-2003 Intel Corp
+ * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>.
+ *
+ * 2001-2005 (c) MontaVista Software, Inc.
+ * Daniel Walker <dwalker@mvista.com>
+ *
+ * (C) 2005 Thomas Gleixner <tglx@linutronix.de>
+ *
+ * Simplifications of the original code by
+ * Oleg Nesterov <oleg@tv-sign.ru>
+ *
+ * Based on simple lists (include/linux/list.h).
+ *
+ * This file contains the add / del functions which are considered to
+ * be too large to inline. See include/linux/plist.h for further
+ * information.
+ */
+
+#include "plist.h"
+#include "bug.h"
+
+#ifdef DEBUG_PLIST
+
+static struct plist_head test_head;
+
+static void plist_check_prev_next(struct list_head *t, struct list_head *p,
+				  struct list_head *n)
+{
+    WARN(n->prev != p || p->next != n,
+         "top: %p, n: %p, p: %p\n"
+         "prev: %p, n: %p, p: %p\n"
+         "next: %p, n: %p, p: %p\n",
+         t, t->next, t->prev,
+         p, p->next, p->prev,
+         n, n->next, n->prev);
+}
+
+static void plist_check_list(struct list_head *top)
+{
+    struct list_head *prev = top, *next = top->next;
+
+    plist_check_prev_next(top, prev, next);
+    while (next != top) {
+        prev = next;
+        next = prev->next;
+        plist_check_prev_next(top, prev, next);
+    }
+}
+
+static void plist_check_head(struct plist_head *head)
+{
+    if (!plist_head_empty(head))
+        plist_check_list(&plist_first(head)->prio_list);
+    plist_check_list(&head->node_list);
+}
+
+#else
+# define plist_check_head(h)	do { } while (0)
+#endif
+
+/**
+ * plist_add - add @node to @head
+ *
+ * @node:	&struct plist_node pointer
+ * @head:	&struct plist_head pointer
+ */
+void plist_add(struct plist_node *node, struct plist_head *head)
+{
+    struct plist_node *first, *iter, *prev = NULL;
+    struct list_head *node_next = &head->node_list;
+
+    plist_check_head(head);
+    WARN_ON(!plist_node_empty(node));
+    WARN_ON(!list_empty(&node->prio_list));
+
+    if (plist_head_empty(head))
+        goto ins_node;
+
+    first = iter = plist_first(head);
+
+    do {
+        if (node->prio < iter->prio) {
+            node_next = &iter->node_list;
+            break;
+        }
+
+        prev = iter;
+        iter = list_entry(iter->prio_list.next,
+                          struct plist_node, prio_list);
+    } while (iter != first);
+
+    if (!prev || prev->prio != node->prio)
+        list_add_tail(&node->prio_list, &iter->prio_list);
+ins_node:
+    list_add_tail(&node->node_list, node_next);
+
+    plist_check_head(head);
+}
+
+/**
+ * plist_del - Remove a @node from plist.
+ *
+ * @node:	&struct plist_node pointer - entry to be removed
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_del(struct plist_node *node, struct plist_head *head)
+{
+    plist_check_head(head);
+
+    if (!list_empty(&node->prio_list)) {
+        if (node->node_list.next != &head->node_list) {
+            struct plist_node *next;
+
+            next = list_entry(node->node_list.next,
+                              struct plist_node, node_list);
+
+            /* add the next plist_node into prio_list */
+            if (list_empty(&next->prio_list))
+                list_add(&next->prio_list, &node->prio_list);
+        }
+        list_del_init(&node->prio_list);
+    }
+
+    list_del_init(&node->node_list);
+
+    plist_check_head(head);
+}
+
+/**
+ * plist_requeue - Requeue @node at end of same-prio entries.
+ *
+ * This is essentially an optimized plist_del() followed by
+ * plist_add().  It moves an entry already in the plist to
+ * after any other same-priority entries.
+ *
+ * @node:	&struct plist_node pointer - entry to be moved
+ * @head:	&struct plist_head pointer - list head
+ */
+void plist_requeue(struct plist_node *node, struct plist_head *head)
+{
+    struct plist_node *iter;
+    struct list_head *node_next = &head->node_list;
+
+    plist_check_head(head);
+    BUG_ON(plist_head_empty(head));
+    BUG_ON(plist_node_empty(node));
+
+    if (node == plist_last(head))
+        return;
+
+    iter = plist_next(node);
+
+    if (node->prio != iter->prio)
+        return;
+
+    plist_del(node, head);
+
+    plist_for_each_continue(iter, head) {
+        if (node->prio != iter->prio) {
+            node_next = &iter->node_list;
+            break;
+        }
+    }
+    list_add_tail(&node->node_list, node_next);
+
+    plist_check_head(head);
+}