/*
* Copyright (C) 2001 Momchil Velikov
* Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2006 Nick Piggin
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
#ifndef _LINUX_RADIX_TREE_H
#define _LINUX_RADIX_TREE_H
-#include <linux/sched.h>
#include <linux/preempt.h>
#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/rcupdate.h>
+/*
+ * An indirect pointer (root->rnode pointing to a radix_tree_node, rather
+ * than a data item) is signalled by the low bit set in the root->rnode
+ * pointer.
+ *
+ * In this case root->height is > 0, but the indirect pointer tests are
+ * needed for RCU lookups (because root->height is unreliable). The only
+ * time callers need worry about this is when doing a lookup_slot under
+ * RCU.
+ */
+#define RADIX_TREE_INDIRECT_PTR 1
+#define RADIX_TREE_RETRY ((void *)-1UL)
+
+static inline void *radix_tree_ptr_to_indirect(void *ptr)
+{
+ return (void *)((unsigned long)ptr | RADIX_TREE_INDIRECT_PTR);
+}
+
+static inline void *radix_tree_indirect_to_ptr(void *ptr)
+{
+ return (void *)((unsigned long)ptr & ~RADIX_TREE_INDIRECT_PTR);
+}
+
+static inline int radix_tree_is_indirect_ptr(void *ptr)
+{
+ return (int)((unsigned long)ptr & RADIX_TREE_INDIRECT_PTR);
+}
+
+/*** radix-tree API starts here ***/
+
+#define RADIX_TREE_MAX_TAGS 2
+
+/* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */
struct radix_tree_root {
unsigned int height;
gfp_t gfp_mask;
(root)->rnode = NULL; \
} while (0)
-#define RADIX_TREE_MAX_TAGS 2
+/**
+ * Radix-tree synchronization
+ *
+ * The radix-tree API requires that users provide all synchronisation (with
+ * specific exceptions, noted below).
+ *
+ * Synchronization of access to the data items being stored in the tree, and
+ * management of their lifetimes must be completely managed by API users.
+ *
+ * For API usage, in general,
+ * - any function _modifying_ the tree or tags (inserting or deleting
+ * items, setting or clearing tags) must exclude other modifications, and
+ * exclude any functions reading the tree.
+ * - any function _reading_ the tree or tags (looking up items or tags,
+ * gang lookups) must exclude modifications to the tree, but may occur
+ * concurrently with other readers.
+ *
+ * The notable exceptions to this rule are the following functions:
+ * radix_tree_lookup
+ * radix_tree_lookup_slot
+ * radix_tree_tag_get
+ * radix_tree_gang_lookup
+ * radix_tree_gang_lookup_slot
+ * radix_tree_gang_lookup_tag
+ * radix_tree_gang_lookup_tag_slot
+ * radix_tree_tagged
+ *
+ * The first 7 functions are able to be called locklessly, using RCU. The
+ * caller must ensure calls to these functions are made within rcu_read_lock()
+ * regions. Other readers (lock-free or otherwise) and modifications may be
+ * running concurrently.
+ *
+ * It is still required that the caller manage the synchronization and lifetimes
+ * of the items. So if RCU lock-free lookups are used, typically this would mean
+ * that the items have their own locks, or are amenable to lock-free access; and
+ * that the items are freed by RCU (or only freed after having been deleted from
+ * the radix tree *and* a synchronize_rcu() grace period).
+ *
+ * (Note, rcu_assign_pointer and rcu_dereference are not needed to control
+ * access to data items when inserting into or looking up from the radix tree)
+ *
+ * Note that the value returned by radix_tree_tag_get() may not be relied upon
+ * if only the RCU read lock is held. Functions to set/clear tags and to
+ * delete nodes running concurrently with it may affect its result such that
+ * two consecutive reads in the same locked section may return different
+ * values. If reliability is required, modification functions must also be
+ * excluded from concurrency.
+ *
+ * radix_tree_tagged is able to be called without locking or RCU.
+ */
+
+/**
+ * radix_tree_deref_slot - dereference a slot
+ * @pslot: pointer to slot, returned by radix_tree_lookup_slot
+ * Returns: item that was stored in that slot with any direct pointer flag
+ * removed.
+ *
+ * For use with radix_tree_lookup_slot(). Caller must hold tree at least read
+ * locked across slot lookup and dereference. More likely, will be used with
+ * radix_tree_replace_slot(), as well, so caller will hold tree write locked.
+ */
+static inline void *radix_tree_deref_slot(void **pslot)
+{
+ void *ret = rcu_dereference(*pslot);
+ if (unlikely(radix_tree_is_indirect_ptr(ret)))
+ ret = RADIX_TREE_RETRY;
+ return ret;
+}
+/**
+ * radix_tree_replace_slot - replace item in a slot
+ * @pslot: pointer to slot, returned by radix_tree_lookup_slot
+ * @item: new item to store in the slot.
+ *
+ * For use with radix_tree_lookup_slot(). Caller must hold tree write locked
+ * across slot lookup and replacement.
+ */
+static inline void radix_tree_replace_slot(void **pslot, void *item)
+{
+ BUG_ON(radix_tree_is_indirect_ptr(item));
+ rcu_assign_pointer(*pslot, item);
+}
int radix_tree_insert(struct radix_tree_root *, unsigned long, void *);
void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
unsigned int
radix_tree_gang_lookup(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items);
+unsigned int
+radix_tree_gang_lookup_slot(struct radix_tree_root *root, void ***results,
+ unsigned long first_index, unsigned int max_items);
+unsigned long radix_tree_next_hole(struct radix_tree_root *root,
+ unsigned long index, unsigned long max_scan);
+unsigned long radix_tree_prev_hole(struct radix_tree_root *root,
+ unsigned long index, unsigned long max_scan);
int radix_tree_preload(gfp_t gfp_mask);
void radix_tree_init(void);
void *radix_tree_tag_set(struct radix_tree_root *root,
radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
unsigned long first_index, unsigned int max_items,
unsigned int tag);
+unsigned int
+radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
+ unsigned long first_index, unsigned int max_items,
+ unsigned int tag);
int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
static inline void radix_tree_preload_end(void)
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff