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/*
* net/tipc/ref.c: TIPC object registry code
*
* Copyright (c) 1991-2006, Ericsson AB
* Copyright (c) 2004-2005, 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"
#include "port.h"
#include "subscr.h"
#include "name_distr.h"
#include "name_table.h"
#include "config.h"
#include "discover.h"
#include "bearer.h"
#include "node.h"
#include "bcast.h"
/*
* Object reference table consists of 2**N entries.
*
* A used entry has object ptr != 0, reference == XXXX|own index
* (XXXX changes each time entry is acquired)
* A free entry has object ptr == 0, reference == YYYY|next free index
* (YYYY is one more than last used XXXX)
*
* Free list is initially chained from entry (2**N)-1 to entry 1.
* Entry 0 is not used to allow index 0 to indicate the end of the free list.
*
* Note: Any accidental reference of the form XXXX|0--0 won't match entry 0
* because entry 0's reference field has the form XXXX|1--1.
*/
struct ref_table tipc_ref_table = { NULL };
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 sz = 1 << 4;
u32 index_mask;
int i;
while (sz < requested_size) {
sz <<= 1;
}
table = vmalloc(sz * sizeof(*table));
if (table == NULL)
return -ENOMEM;
write_lock_bh(&ref_table_lock);
index_mask = sz - 1;
for (i = sz - 1; i >= 0; i--) {
table[i].object = NULL;
spin_lock_init(&table[i].lock);
table[i].data.next_plus_upper = (start & ~index_mask) + i - 1;
}
tipc_ref_table.entries = table;
tipc_ref_table.index_mask = index_mask;
tipc_ref_table.first_free = sz - 1;
tipc_ref_table.last_free = 1;
write_unlock_bh(&ref_table_lock);
return TIPC_OK;
}
/**
* 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
*
* Return a unique reference value which can be translated back to the pointer
* 'object' at a later time. Also, pass back a pointer to the lock protecting
* the object, but without locking it.
*/
u32 tipc_ref_acquire(void *object, spinlock_t **lock)
{
struct reference *entry;
u32 index;
u32 index_mask;
u32 next_plus_upper;
u32 reference = 0;
if (!object) {
err("Attempt to acquire reference to non-existent object\n");
return 0;
}
if (!tipc_ref_table.entries) {
err("Reference table not found during acquisition attempt\n");
return 0;
}
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;
/* take lock in case a previous user of entry still holds it */
spin_lock_bh(&entry->lock);
next_plus_upper = entry->data.next_plus_upper;
tipc_ref_table.first_free = next_plus_upper & index_mask;
reference = (next_plus_upper & ~index_mask) + index;
entry->data.reference = reference;
entry->object = object;
if (lock != 0)
*lock = &entry->lock;
spin_unlock_bh(&entry->lock);
}
write_unlock_bh(&ref_table_lock);
return reference;
}
/**
* 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 (!ref) {
err("Attempt to discard reference 0\n");
return;
}
if (!tipc_ref_table.entries) {
err("Reference table not found during discard attempt\n");
return;
}
write_lock_bh(&ref_table_lock);
index_mask = tipc_ref_table.index_mask;
index = ref & index_mask;
entry = &(tipc_ref_table.entries[index]);
if (!entry->object) {
err("Attempt to discard reference to non-existent object\n");
goto exit;
}
if (entry->data.reference != ref) {
err("Attempt to discard non-existent reference\n");
goto exit;
}
/* mark entry as unused */
entry->object = NULL;
if (tipc_ref_table.first_free == 0)
tipc_ref_table.first_free = index;
else
/* next_plus_upper is always XXXX|0--0 for last free entry */
tipc_ref_table.entries[tipc_ref_table.last_free].data.next_plus_upper
|= index;
tipc_ref_table.last_free = index;
/* increment upper bits of entry to invalidate subsequent references */
entry->data.next_plus_upper = (ref & ~index_mask) + (index_mask + 1);
exit:
write_unlock_bh(&ref_table_lock);
}
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