1 files changed, 299 insertions, 0 deletions
diff --git a/net/tipc/ref.c b/net/tipc/ref.c
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+/*
+ * net/tipc/ref.c: TIPC object registry code
+ *
+ * Copyright (c) 1991-2006, Ericsson AB
+ * Copyright (c) 2004-2007, Wind River Systems
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "core.h"
+#include "ref.h"
+
+/**
+ * struct reference - TIPC object reference entry
+ * @object: pointer to object associated with reference entry
+ * @lock: spinlock controlling access to object
+ * @ref: reference value for object (combines instance & array index info)
+ */
+
+struct reference {
+	void *object;
+	spinlock_t lock;
+	u32 ref;
+};
+
+/**
+ * struct tipc_ref_table - table of TIPC object reference entries
+ * @entries: pointer to array of reference entries
+ * @capacity: array index of first unusable entry
+ * @init_point: array index of first uninitialized entry
+ * @first_free: array index of first unused object reference entry
+ * @last_free: array index of last unused object reference entry
+ * @index_mask: bitmask for array index portion of reference values
+ * @start_mask: initial value for instance value portion of reference values
+ */
+
+struct ref_table {
+	struct reference *entries;
+	u32 capacity;
+	u32 init_point;
+	u32 first_free;
+	u32 last_free;
+	u32 index_mask;
+	u32 start_mask;
+};
+
+/*
+ * Object reference table consists of 2**N entries.
+ *
+ * State	Object ptr	Reference
+ * -----        ----------      ---------
+ * In use        non-NULL       XXXX|own index
+ *				(XXXX changes each time entry is acquired)
+ * Free            NULL         YYYY|next free index
+ *				(YYYY is one more than last used XXXX)
+ * Uninitialized   NULL         0
+ *
+ * Entry 0 is not used; this allows index 0 to denote the end of the free list.
+ *
+ * Note that a reference value of 0 does not necessarily indicate that an
+ * entry is uninitialized, since the last entry in the free list could also
+ * have a reference value of 0 (although this is unlikely).
+ */
+
+static struct ref_table tipc_ref_table;
+
+static DEFINE_RWLOCK(ref_table_lock);
+
+/**
+ * tipc_ref_table_init - create reference table for objects
+ */
+
+int tipc_ref_table_init(u32 requested_size, u32 start)
+{
+	struct reference *table;
+	u32 actual_size;
+
+	/* account for unused entry, then round up size to a power of 2 */
+
+	requested_size++;
+	for (actual_size = 16; actual_size < requested_size; actual_size <<= 1)
+		/* do nothing */ ;
+
+	/* allocate table & mark all entries as uninitialized */
+
+	table = vzalloc(actual_size * sizeof(struct reference));
+	if (table == NULL)
+		return -ENOMEM;
+
+	tipc_ref_table.entries = table;
+	tipc_ref_table.capacity = requested_size;
+	tipc_ref_table.init_point = 1;
+	tipc_ref_table.first_free = 0;
+	tipc_ref_table.last_free = 0;
+	tipc_ref_table.index_mask = actual_size - 1;
+	tipc_ref_table.start_mask = start & ~tipc_ref_table.index_mask;
+
+	return 0;
+}
+
+/**
+ * tipc_ref_table_stop - destroy reference table for objects
+ */
+
+void tipc_ref_table_stop(void)
+{
+	if (!tipc_ref_table.entries)
+		return;
+
+	vfree(tipc_ref_table.entries);
+	tipc_ref_table.entries = NULL;
+}
+
+/**
+ * tipc_ref_acquire - create reference to an object
+ *
+ * Register an object pointer in reference table and lock the object.
+ * Returns a unique reference value that is used from then on to retrieve the
+ * object pointer, or to determine that the object has been deregistered.
+ *
+ * Note: The object is returned in the locked state so that the caller can
+ * register a partially initialized object, without running the risk that
+ * the object will be accessed before initialization is complete.
+ */
+
+u32 tipc_ref_acquire(void *object, spinlock_t **lock)
+{
+	u32 index;
+	u32 index_mask;
+	u32 next_plus_upper;
+	u32 ref;
+	struct reference *entry = NULL;
+
+	if (!object) {
+		err("Attempt to acquire reference to non-existent object\n");
+		return 0;
+	}
+	if (!tipc_ref_table.entries) {
+		err("Reference table not found during acquisition attempt\n");
+		return 0;
+	}
+
+	/* take a free entry, if available; otherwise initialize a new entry */
+
+	write_lock_bh(&ref_table_lock);
+	if (tipc_ref_table.first_free) {
+		index = tipc_ref_table.first_free;
+		entry = &(tipc_ref_table.entries[index]);
+		index_mask = tipc_ref_table.index_mask;
+		next_plus_upper = entry->ref;
+		tipc_ref_table.first_free = next_plus_upper & index_mask;
+		ref = (next_plus_upper & ~index_mask) + index;
+	} else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
+		index = tipc_ref_table.init_point++;
+		entry = &(tipc_ref_table.entries[index]);
+		spin_lock_init(&entry->lock);
+		ref = tipc_ref_table.start_mask + index;
+	} else {
+		ref = 0;
+	}
+	write_unlock_bh(&ref_table_lock);
+
+	/*
+	 * Grab the lock so no one else can modify this entry
+	 * While we assign its ref value & object pointer
+	 */
+	if (entry) {
+		spin_lock_bh(&entry->lock);
+		entry->ref = ref;
+		entry->object = object;
+		*lock = &entry->lock;
+		/*
+		 * keep it locked, the caller is responsible
+		 * for unlocking this when they're done with it
+		 */
+	}
+
+	return ref;
+}
+
+/**
+ * tipc_ref_discard - invalidate references to an object
+ *
+ * Disallow future references to an object and free up the entry for re-use.
+ * Note: The entry's spin_lock may still be busy after discard
+ */
+
+void tipc_ref_discard(u32 ref)
+{
+	struct reference *entry;
+	u32 index;
+	u32 index_mask;
+
+	if (!tipc_ref_table.entries) {
+		err("Reference table not found during discard attempt\n");
+		return;
+	}
+
+	index_mask = tipc_ref_table.index_mask;
+	index = ref & index_mask;
+	entry = &(tipc_ref_table.entries[index]);
+
+	write_lock_bh(&ref_table_lock);
+
+	if (!entry->object) {
+		err("Attempt to discard reference to non-existent object\n");
+		goto exit;
+	}
+	if (entry->ref != ref) {
+		err("Attempt to discard non-existent reference\n");
+		goto exit;
+	}
+
+	/*
+	 * mark entry as unused; increment instance part of entry's reference
+	 * to invalidate any subsequent references
+	 */
+
+	entry->object = NULL;
+	entry->ref = (ref & ~index_mask) + (index_mask + 1);
+
+	/* append entry to free entry list */
+
+	if (tipc_ref_table.first_free == 0)
+		tipc_ref_table.first_free = index;
+	else
+		tipc_ref_table.entries[tipc_ref_table.last_free].ref |= index;
+	tipc_ref_table.last_free = index;
+
+exit:
+	write_unlock_bh(&ref_table_lock);
+}
+
+/**
+ * tipc_ref_lock - lock referenced object and return pointer to it
+ */
+
+void *tipc_ref_lock(u32 ref)
+{
+	if (likely(tipc_ref_table.entries)) {
+		struct reference *entry;
+
+		entry = &tipc_ref_table.entries[ref &
+						tipc_ref_table.index_mask];
+		if (likely(entry->ref != 0)) {
+			spin_lock_bh(&entry->lock);
+			if (likely((entry->ref == ref) && (entry->object)))
+				return entry->object;
+			spin_unlock_bh(&entry->lock);
+		}
+	}
+	return NULL;
+}
+
+
+/**
+ * tipc_ref_deref - return pointer referenced object (without locking it)
+ */
+
+void *tipc_ref_deref(u32 ref)
+{
+	if (likely(tipc_ref_table.entries)) {
+		struct reference *entry;
+
+		entry = &tipc_ref_table.entries[ref &
+						tipc_ref_table.index_mask];
+		if (likely(entry->ref == ref))
+			return entry->object;
+	}
+	return NULL;
+}
+