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 rwlock_t ref_table_lock = RW_LOCK_UNLOCKED;
  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 = (struct reference *)vmalloc(sz * sizeof(struct reference));
  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                 table[i].lock = SPIN_LOCK_UNLOCKED;
  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         assert(tipc_ref_table.entries && object);
 131
 132         write_lock_bh(&ref_table_lock);
 133         if (tipc_ref_table.first_free) {
 134                 index = tipc_ref_table.first_free;
 135                 entry = &(tipc_ref_table.entries[index]);
 136                 index_mask = tipc_ref_table.index_mask;
 137                 /* take lock in case a previous user of entry still holds it */
 138                 spin_lock_bh(&entry->lock);
 139                 next_plus_upper = entry->data.next_plus_upper;
 140                 tipc_ref_table.first_free = next_plus_upper & index_mask;
 141                 reference = (next_plus_upper & ~index_mask) + index;
 142                 entry->data.reference = reference;
 143                 entry->object = object;
 144                 if (lock != 0)
 145                         *lock = &entry->lock;
 146                 spin_unlock_bh(&entry->lock);
 147         }
 148         write_unlock_bh(&ref_table_lock);
 149         return reference;
 150 }
 151
 152 /**
 153  * tipc_ref_discard - invalidate references to an object
 154  *
 155  * Disallow future references to an object and free up the entry for re-use.
 156  * Note: The entry's spin_lock may still be busy after discard
 157  */
 158
 159 void tipc_ref_discard(u32 ref)
 160 {
 161         struct reference *entry;
 162         u32 index;
 163         u32 index_mask;
 164
 165         assert(tipc_ref_table.entries);
 166         assert(ref != 0);
 167
 168         write_lock_bh(&ref_table_lock);
 169         index_mask = tipc_ref_table.index_mask;
 170         index = ref & index_mask;
 171         entry = &(tipc_ref_table.entries[index]);
 172         assert(entry->object != 0);
 173         assert(entry->data.reference == ref);
 174
 175         /* mark entry as unused */
 176         entry->object = NULL;
 177         if (tipc_ref_table.first_free == 0)
 178                 tipc_ref_table.first_free = index;
 179         else
 180                 /* next_plus_upper is always XXXX|0--0 for last free entry */
 181                 tipc_ref_table.entries[tipc_ref_table.last_free].data.next_plus_upper
 182                         |= index;
 183         tipc_ref_table.last_free = index;
 184
 185         /* increment upper bits of entry to invalidate subsequent references */
 186         entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
 187         write_unlock_bh(&ref_table_lock);
 188 }
 189