net/tipc/ref.c

   1 /*
   2  * net/tipc/ref.c: TIPC object registry code
   3  *
   4  * Copyright (c) 1991-2006, Ericsson AB
   5  * Copyright (c) 2004-2005, Wind River Systems
   6  * All rights reserved.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. Neither the names of the copyright holders nor the names of its
  17  *    contributors may be used to endorse or promote products derived from
  18  *    this software without specific prior written permission.
  19  *
  20  * Alternatively, this software may be distributed under the terms of the
  21  * GNU General Public License ("GPL") version 2 as published by the Free
  22  * Software Foundation.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  25  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  28  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  29  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  30  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  31  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  32  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  33  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  34  * POSSIBILITY OF SUCH DAMAGE.
  35  */
  36
  37 #include "core.h"
  38 #include "ref.h"
  39 #include "port.h"
  40 #include "subscr.h"
  41 #include "name_distr.h"
  42 #include "name_table.h"
  43 #include "config.h"
  44 #include "discover.h"
  45 #include "bearer.h"
  46 #include "node.h"
  47 #include "bcast.h"
  48
  49 /*
  50  * Object reference table consists of 2**N entries.
  51  *
  52  * A used entry has object ptr != 0, reference == XXXX|own index
  53  *                                   (XXXX changes each time entry is acquired)
  54  * A free entry has object ptr == 0, reference == YYYY|next free index
  55  *                                   (YYYY is one more than last used XXXX)
  56  *
  57  * Free list is initially chained from entry (2**N)-1 to entry 1.
  58  * Entry 0 is not used to allow index 0 to indicate the end of the free list.
  59  *
  60  * Note: Any accidental reference of the form XXXX|0--0 won't match entry 0
  61  * because entry 0's reference field has the form XXXX|1--1.
  62  */
  63
  64 struct ref_table tipc_ref_table = { NULL };
  65
  66 static DEFINE_RWLOCK(ref_table_lock);
  67
  68 /**
  69  * tipc_ref_table_init - create reference table for objects
  70  */
  71
  72 int tipc_ref_table_init(u32 requested_size, u32 start)
  73 {
  74         struct reference *table;
  75         u32 sz = 1 << 4;
  76         u32 index_mask;
  77         int i;
  78
  79         while (sz < requested_size) {
  80                 sz <<= 1;
  81         }
  82         table = vmalloc(sz * sizeof(*table));
  83         if (table == NULL)
  84                 return -ENOMEM;
  85
  86         write_lock_bh(&ref_table_lock);
  87         index_mask = sz - 1;
  88         for (i = sz - 1; i >= 0; i--) {
  89                 table[i].object = NULL;
  90                 spin_lock_init(&table[i].lock);
  91                 table[i].data.next_plus_upper = (start & ~index_mask) + i - 1;
  92         }
  93         tipc_ref_table.entries = table;
  94         tipc_ref_table.index_mask = index_mask;
  95         tipc_ref_table.first_free = sz - 1;
  96         tipc_ref_table.last_free = 1;
  97         write_unlock_bh(&ref_table_lock);
  98         return TIPC_OK;
  99 }
 100
 101 /**
 102  * tipc_ref_table_stop - destroy reference table for objects
 103  */
 104
 105 void tipc_ref_table_stop(void)
 106 {
 107         if (!tipc_ref_table.entries)
 108                 return;
 109
 110         vfree(tipc_ref_table.entries);
 111         tipc_ref_table.entries = NULL;
 112 }
 113
 114 /**
 115  * tipc_ref_acquire - create reference to an object
 116  *
 117  * Return a unique reference value which can be translated back to the pointer
 118  * 'object' at a later time.  Also, pass back a pointer to the lock protecting
 119  * the object, but without locking it.
 120  */
 121
 122 u32 tipc_ref_acquire(void *object, spinlock_t **lock)
 123 {
 124         struct reference *entry;
 125         u32 index;
 126         u32 index_mask;
 127         u32 next_plus_upper;
 128         u32 reference = 0;
 129
 130         if (!object) {
 131                 err("Attempt to acquire reference to non-existent object\n");
 132                 return 0;
 133         }
 134         if (!tipc_ref_table.entries) {
 135                 err("Reference table not found during acquisition attempt\n");
 136                 return 0;
 137         }
 138
 139         write_lock_bh(&ref_table_lock);
 140         if (tipc_ref_table.first_free) {
 141                 index = tipc_ref_table.first_free;
 142                 entry = &(tipc_ref_table.entries[index]);
 143                 index_mask = tipc_ref_table.index_mask;
 144                 /* take lock in case a previous user of entry still holds it */
 145                 spin_lock_bh(&entry->lock);
 146                 next_plus_upper = entry->data.next_plus_upper;
 147                 tipc_ref_table.first_free = next_plus_upper & index_mask;
 148                 reference = (next_plus_upper & ~index_mask) + index;
 149                 entry->data.reference = reference;
 150                 entry->object = object;
 151                 if (lock != 0)
 152                         *lock = &entry->lock;
 153                 spin_unlock_bh(&entry->lock);
 154         }
 155         write_unlock_bh(&ref_table_lock);
 156         return reference;
 157 }
 158
 159 /**
 160  * tipc_ref_discard - invalidate references to an object
 161  *
 162  * Disallow future references to an object and free up the entry for re-use.
 163  * Note: The entry's spin_lock may still be busy after discard
 164  */
 165
 166 void tipc_ref_discard(u32 ref)
 167 {
 168         struct reference *entry;
 169         u32 index;
 170         u32 index_mask;
 171
 172         if (!ref) {
 173                 err("Attempt to discard reference 0\n");
 174                 return;
 175         }
 176         if (!tipc_ref_table.entries) {
 177                 err("Reference table not found during discard attempt\n");
 178                 return;
 179         }
 180
 181         write_lock_bh(&ref_table_lock);
 182         index_mask = tipc_ref_table.index_mask;
 183         index = ref & index_mask;
 184         entry = &(tipc_ref_table.entries[index]);
 185
 186         if (!entry->object) {
 187                 err("Attempt to discard reference to non-existent object\n");
 188                 goto exit;
 189         }
 190         if (entry->data.reference != ref) {
 191                 err("Attempt to discard non-existent reference\n");
 192                 goto exit;
 193         }
 194
 195         /* mark entry as unused */
 196         entry->object = NULL;
 197         if (tipc_ref_table.first_free == 0)
 198                 tipc_ref_table.first_free = index;
 199         else
 200                 /* next_plus_upper is always XXXX|0--0 for last free entry */
 201                 tipc_ref_table.entries[tipc_ref_table.last_free].data.next_plus_upper
 202                         |= index;
 203         tipc_ref_table.last_free = index;
 204
 205         /* increment upper bits of entry to invalidate subsequent references */
 206         entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
 207 exit:
 208         write_unlock_bh(&ref_table_lock);
 209 }
 210