[PATCH] pi-futex: add plist implementation

Add the priority-sorted list (plist) implementation.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 125 insertions, 0 deletions

diff --git a/lib/Kconfig b/lib/Kconfig
index 3de93357f5ab..f6299342b882 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -86,4 +86,10 @@ config TEXTSEARCH_BM
 config TEXTSEARCH_FSM
         tristate
 
+#
+# plist support is select#ed if needed
+#
+config PLIST
+        boolean
+
 endmenu
diff --git a/lib/Makefile b/lib/Makefile
index 79358ad1f113..10c13c9d7824 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -25,6 +25,7 @@ lib-$(CONFIG_SEMAPHORE_SLEEPERS) += semaphore-sleepers.o
 lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
 lib-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
 obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
+obj-$(CONFIG_PLIST) += plist.o
 obj-$(CONFIG_DEBUG_PREEMPT) += smp_processor_id.o
 
 ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
diff --git a/lib/plist.c b/lib/plist.c
new file mode 100644
index 000000000000..3074a02272f3
--- /dev/null
+++ b/lib/plist.c
@@ -0,0 +1,118 @@
+/*
+ * 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>
+ *
+ * Licensed under the FSF's GNU Public License v2 or later.
+ *
+ * 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 <linux/plist.h>
+#include <linux/spinlock.h>
+
+#ifdef CONFIG_DEBUG_PI_LIST
+
+static void plist_check_prev_next(struct list_head *t, struct list_head *p,
+                                  struct list_head *n)
+{
+        if (n->prev != p || p->next != n) {
+                printk("top: %p, n: %p, p: %p\n", t, t->next, t->prev);
+                printk("prev: %p, n: %p, p: %p\n", p, p->next, p->prev);
+                printk("next: %p, n: %p, p: %p\n", n, n->next, n->prev);
+                WARN_ON(1);
+        }
+}
+
+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)
+{
+        WARN_ON(!head->lock);
+        if (head->lock)
+                WARN_ON_SMP(!spin_is_locked(head->lock));
+        plist_check_list(&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 *iter;
+
+        plist_check_head(head);
+        WARN_ON(!plist_node_empty(node));
+
+        list_for_each_entry(iter, &head->prio_list, plist.prio_list) {
+                if (node->prio < iter->prio)
+                        goto lt_prio;
+                else if (node->prio == iter->prio) {
+                        iter = list_entry(iter->plist.prio_list.next,
+                                        struct plist_node, plist.prio_list);
+                        goto eq_prio;
+                }
+        }
+
+lt_prio:
+        list_add_tail(&node->plist.prio_list, &iter->plist.prio_list);
+eq_prio:
+        list_add_tail(&node->plist.node_list, &iter->plist.node_list);
+
+        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->plist.prio_list)) {
+                struct plist_node *next = plist_first(&node->plist);
+
+                list_move_tail(&next->plist.prio_list, &node->plist.prio_list);
+                list_del_init(&node->plist.prio_list);
+        }
+
+        list_del_init(&node->plist.node_list);
+
+        plist_check_head(head);
+}