[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>

4 files changed, 372 insertions, 0 deletions

diff --git a/include/linux/plist.h b/include/linux/plist.h
new file mode 100644
index 000000000000..3404faef542c
--- /dev/null
+++ b/include/linux/plist.h
@@ -0,0 +1,247 @@
+/*
+ * 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 is a priority-sorted list of nodes; each node has a
+ * priority from INT_MIN (highest) to INT_MAX (lowest).
+ *
+ * Addition is O(K), removal is O(1), change of priority of a node is
+ * O(K) and K is the number of RT priority levels used in the system.
+ * (1 <= K <= 99)
+ *
+ * This list is really a list of lists:
+ *
+ *  - The tier 1 list is the prio_list, different priority nodes.
+ *
+ *  - The tier 2 list is the node_list, serialized nodes.
+ *
+ * Simple ASCII art explanation:
+ *
+ * |HEAD          |
+ * |              |
+ * |prio_list.prev|<------------------------------------|
+ * |prio_list.next|<->|pl|<->|pl|<--------------->|pl|<-|
+ * |10            |   |10|   |21|   |21|   |21|   |40|   (prio)
+ * |              |   |  |   |  |   |  |   |  |   |  |
+ * |              |   |  |   |  |   |  |   |  |   |  |
+ * |node_list.next|<->|nl|<->|nl|<->|nl|<->|nl|<->|nl|<-|
+ * |node_list.prev|<------------------------------------|
+ *
+ * The nodes on the prio_list list are sorted by priority to simplify
+ * the insertion of new nodes. There are no nodes with duplicate
+ * priorites on the list.
+ *
+ * The nodes on the node_list is ordered by priority and can contain
+ * entries which have the same priority. Those entries are ordered
+ * FIFO
+ *
+ * Addition means: look for the prio_list node in the prio_list
+ * for the priority of the node and insert it before the node_list
+ * entry of the next prio_list node. If it is the first node of
+ * that priority, add it to the prio_list in the right position and
+ * insert it into the serialized node_list list
+ *
+ * Removal means remove it from the node_list and remove it from
+ * the prio_list if the node_list list_head is non empty. In case
+ * of removal from the prio_list it must be checked whether other
+ * entries of the same priority are on the list or not. If there
+ * is another entry of the same priority then this entry has to
+ * replace the removed entry on the prio_list. If the entry which
+ * is removed is the only entry of this priority then a simple
+ * remove from both list is sufficient.
+ *
+ * INT_MIN is the highest priority, 0 is the medium highest, INT_MAX
+ * is lowest priority.
+ *
+ * No locking is done, up to the caller.
+ *
+ */
+#ifndef _LINUX_PLIST_H_
+#define _LINUX_PLIST_H_
+
+#include <linux/list.h>
+#include <linux/spinlock_types.h>
+
+struct plist_head {
+        struct list_head prio_list;
+        struct list_head node_list;
+#ifdef CONFIG_DEBUG_PI_LIST
+        spinlock_t *lock;
+#endif
+};
+
+struct plist_node {
+        int                     prio;
+        struct plist_head       plist;
+};
+
+#ifdef CONFIG_DEBUG_PI_LIST
+# define PLIST_HEAD_LOCK_INIT(_lock)    .lock = _lock
+#else
+# define PLIST_HEAD_LOCK_INIT(_lock)
+#endif
+
+/**
+ * #PLIST_HEAD_INIT - static struct plist_head initializer
+ *
+ * @head:       struct plist_head variable name
+ */
+#define PLIST_HEAD_INIT(head, _lock)                    \
+{                                                       \
+        .prio_list = LIST_HEAD_INIT((head).prio_list),  \
+        .node_list = LIST_HEAD_INIT((head).node_list),  \
+        PLIST_HEAD_LOCK_INIT(&(_lock))                  \
+}
+
+/**
+ * #PLIST_NODE_INIT - static struct plist_node initializer
+ *
+ * @node:       struct plist_node variable name
+ * @__prio:     initial node priority
+ */
+#define PLIST_NODE_INIT(node, __prio)                   \
+{                                                       \
+        .prio  = (__prio),                              \
+        .plist = PLIST_HEAD_INIT((node).plist, NULL),   \
+}
+
+/**
+ * plist_head_init - dynamic struct plist_head initializer
+ *
+ * @head:       &struct plist_head pointer
+ */
+static inline void
+plist_head_init(struct plist_head *head, spinlock_t *lock)
+{
+        INIT_LIST_HEAD(&head->prio_list);
+        INIT_LIST_HEAD(&head->node_list);
+#ifdef CONFIG_DEBUG_PI_LIST
+        head->lock = lock;
+#endif
+}
+
+/**
+ * plist_node_init - Dynamic struct plist_node initializer
+ *
+ * @node:       &struct plist_node pointer
+ * @prio:       initial node priority
+ */
+static inline void plist_node_init(struct plist_node *node, int prio)
+{
+        node->prio = prio;
+        plist_head_init(&node->plist, NULL);
+}
+
+extern void plist_add(struct plist_node *node, struct plist_head *head);
+extern void plist_del(struct plist_node *node, struct plist_head *head);
+
+/**
+ * plist_for_each - iterate over the plist
+ *
+ * @pos1:       the type * to use as a loop counter.
+ * @head:       the head for your list.
+ */
+#define plist_for_each(pos, head)       \
+         list_for_each_entry(pos, &(head)->node_list, plist.node_list)
+
+/**
+ * plist_for_each_entry_safe - iterate over a plist of given type safe
+ * against removal of list entry
+ *
+ * @pos1:       the type * to use as a loop counter.
+ * @n1: another type * to use as temporary storage
+ * @head:       the head for your list.
+ */
+#define plist_for_each_safe(pos, n, head)       \
+         list_for_each_entry_safe(pos, n, &(head)->node_list, plist.node_list)
+
+/**
+ * plist_for_each_entry - iterate over list of given type
+ *
+ * @pos:        the type * to use as a loop counter.
+ * @head:       the head for your list.
+ * @member:     the name of the list_struct within the struct.
+ */
+#define plist_for_each_entry(pos, head, mem)    \
+         list_for_each_entry(pos, &(head)->node_list, mem.plist.node_list)
+
+/**
+ * plist_for_each_entry_safe - iterate over list of given type safe against
+ * removal of list entry
+ *
+ * @pos:        the type * to use as a loop counter.
+ * @n:          another type * to use as temporary storage
+ * @head:       the head for your list.
+ * @m:          the name of the list_struct within the struct.
+ */
+#define plist_for_each_entry_safe(pos, n, head, m)      \
+        list_for_each_entry_safe(pos, n, &(head)->node_list, m.plist.node_list)
+
+/**
+ * plist_head_empty - return !0 if a plist_head is empty
+ *
+ * @head:       &struct plist_head pointer
+ */
+static inline int plist_head_empty(const struct plist_head *head)
+{
+        return list_empty(&head->node_list);
+}
+
+/**
+ * plist_node_empty - return !0 if plist_node is not on a list
+ *
+ * @node:       &struct plist_node pointer
+ */
+static inline int plist_node_empty(const struct plist_node *node)
+{
+        return plist_head_empty(&node->plist);
+}
+
+/* All functions below assume the plist_head is not empty. */
+
+/**
+ * plist_first_entry - get the struct for the first entry
+ *
+ * @ptr:        the &struct plist_head pointer.
+ * @type:       the type of the struct this is embedded in.
+ * @member:     the name of the list_struct within the struct.
+ */
+#ifdef CONFIG_DEBUG_PI_LIST
+# define plist_first_entry(head, type, member)  \
+({ \
+        WARN_ON(plist_head_empty(head)); \
+        container_of(plist_first(head), type, member); \
+})
+#else
+# define plist_first_entry(head, type, member)  \
+        container_of(plist_first(head), type, member)
+#endif
+
+/**
+ * plist_first - return the first node (and thus, highest priority)
+ *
+ * @head:       the &struct plist_head pointer
+ *
+ * Assumes the plist is _not_ empty.
+ */
+static inline struct plist_node* plist_first(const struct plist_head *head)
+{
+        return list_entry(head->node_list.next,
+                          struct plist_node, plist.node_list);
+}
+
+#endif
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);
+}