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