/* * 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) {		pr_err("Attempt to acquire ref. to non-existent obj\n");		return 0;	}	if (!tipc_ref_table.entries) {		pr_err("Ref. table not found in 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) {		pr_err("Ref. 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) {		pr_err("Attempt to discard ref. to non-existent obj\n");		goto exit;	}	if (entry->ref != ref) {		pr_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;}