net/tipc/ref.c

   1 /*
   2  * net/tipc/ref.c: TIPC object registry code
   3  *
   4  * Copyright (c) 2003-2005, Ericsson Research Canada
   5  * Copyright (c) 2004-2005, Wind River Systems
   6  * Copyright (c) 2005-2006, Ericsson AB
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions are met:
  11  *
  12  * Redistributions of source code must retain the above copyright notice, this
  13  * list of conditions and the following disclaimer.
  14  * Redistributions in binary form must reproduce the above copyright notice,
  15  * this list of conditions and the following disclaimer in the documentation
  16  * and/or other materials provided with the distribution.
  17  * Neither the names of the copyright holders nor the names of its
  18  * contributors may be used to endorse or promote products derived from this
  19  * software without specific prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  22  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  24  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  25  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  26  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  27  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  28  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  29  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  30  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  31  * POSSIBILITY OF SUCH DAMAGE.
  32  */
  33
  34 #include "core.h"
  35 #include "ref.h"
  36 #include "port.h"
  37 #include "subscr.h"
  38 #include "name_distr.h"
  39 #include "name_table.h"
  40 #include "config.h"
  41 #include "discover.h"
  42 #include "bearer.h"
  43 #include "node.h"
  44 #include "bcast.h"
  45
  46 /*
  47  * Object reference table consists of 2**N entries.
  48  *
  49  * A used entry has object ptr != 0, reference == XXXX|own index
  50  *                                   (XXXX changes each time entry is acquired)
  51  * A free entry has object ptr == 0, reference == YYYY|next free index
  52  *                                   (YYYY is one more than last used XXXX)
  53  *
  54  * Free list is initially chained from entry (2**N)-1 to entry 1.
  55  * Entry 0 is not used to allow index 0 to indicate the end of the free list.
  56  *
  57  * Note: Any accidental reference of the form XXXX|0--0 won't match entry 0
  58  * because entry 0's reference field has the form XXXX|1--1.
  59  */
  60
  61 struct ref_table ref_table = { 0 };
  62
  63 rwlock_t reftbl_lock = RW_LOCK_UNLOCKED;
  64
  65 /**
  66  * ref_table_init - create reference table for objects
  67  */
  68
  69 int ref_table_init(u32 requested_size, u32 start)
  70 {
  71         struct reference *table;
  72         u32 sz = 1 << 4;
  73         u32 index_mask;
  74         int i;
  75
  76         while (sz < requested_size) {
  77                 sz <<= 1;
  78         }
  79         table = (struct reference *)vmalloc(sz * sizeof(struct reference));
  80         if (table == NULL)
  81                 return -ENOMEM;
  82
  83         write_lock_bh(&reftbl_lock);
  84         index_mask = sz - 1;
  85         for (i = sz - 1; i >= 0; i--) {
  86                 table[i].object = 0;
  87                 table[i].lock = SPIN_LOCK_UNLOCKED;
  88                 table[i].data.next_plus_upper = (start & ~index_mask) + i - 1;
  89         }
  90         ref_table.entries = table;
  91         ref_table.index_mask = index_mask;
  92         ref_table.first_free = sz - 1;
  93         ref_table.last_free = 1;
  94         write_unlock_bh(&reftbl_lock);
  95         return TIPC_OK;
  96 }
  97
  98 /**
  99  * ref_table_stop - destroy reference table for objects
 100  */
 101
 102 void ref_table_stop(void)
 103 {
 104         if (!ref_table.entries)
 105                 return;
 106
 107         vfree(ref_table.entries);
 108         ref_table.entries = 0;
 109 }
 110
 111 /**
 112  * ref_acquire - create reference to an object
 113  *
 114  * Return a unique reference value which can be translated back to the pointer
 115  * 'object' at a later time.  Also, pass back a pointer to the lock protecting
 116  * the object, but without locking it.
 117  */
 118
 119 u32 ref_acquire(void *object, spinlock_t **lock)
 120 {
 121         struct reference *entry;
 122         u32 index;
 123         u32 index_mask;
 124         u32 next_plus_upper;
 125         u32 reference = 0;
 126
 127         assert(ref_table.entries && object);
 128
 129         write_lock_bh(&reftbl_lock);
 130         if (ref_table.first_free) {
 131                 index = ref_table.first_free;
 132                 entry = &(ref_table.entries[index]);
 133                 index_mask = ref_table.index_mask;
 134                 /* take lock in case a previous user of entry still holds it */
 135                 spin_lock_bh(&entry->lock);
 136                 next_plus_upper = entry->data.next_plus_upper;
 137                 ref_table.first_free = next_plus_upper & index_mask;
 138                 reference = (next_plus_upper & ~index_mask) + index;
 139                 entry->data.reference = reference;
 140                 entry->object = object;
 141                 if (lock != 0)
 142                         *lock = &entry->lock;
 143                 spin_unlock_bh(&entry->lock);
 144         }
 145         write_unlock_bh(&reftbl_lock);
 146         return reference;
 147 }
 148
 149 /**
 150  * ref_discard - invalidate references to an object
 151  *
 152  * Disallow future references to an object and free up the entry for re-use.
 153  * Note: The entry's spin_lock may still be busy after discard
 154  */
 155
 156 void ref_discard(u32 ref)
 157 {
 158         struct reference *entry;
 159         u32 index;
 160         u32 index_mask;
 161
 162         assert(ref_table.entries);
 163         assert(ref != 0);
 164
 165         write_lock_bh(&reftbl_lock);
 166         index_mask = ref_table.index_mask;
 167         index = ref & index_mask;
 168         entry = &(ref_table.entries[index]);
 169         assert(entry->object != 0);
 170         assert(entry->data.reference == ref);
 171
 172         /* mark entry as unused */
 173         entry->object = 0;
 174         if (ref_table.first_free == 0)
 175                 ref_table.first_free = index;
 176         else
 177                 /* next_plus_upper is always XXXX|0--0 for last free entry */
 178                 ref_table.entries[ref_table.last_free].data.next_plus_upper
 179                         |= index;
 180         ref_table.last_free = index;
 181
 182         /* increment upper bits of entry to invalidate subsequent references */
 183         entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
 184         write_unlock_bh(&reftbl_lock);
 185 }
 186