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/*
* net/tipc/ref.c: TIPC object registry code
*
* Copyright (c) 1991-2006, Ericsson AB
* Copyright (c) 2004-2007, 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"
/**
* struct reference - TIPC object reference entry
* @object: pointer to object associated with reference entry
* @lock: spinlock controlling access to object
* @ref: reference value for object (combines instance & array index info)
*/
struct reference {
void *object;
spinlock_t lock;
u32 ref;
};
/**
* struct tipc_ref_table - table of TIPC object reference entries
* @entries: pointer to array of reference entries
* @capacity: array index of first unusable entry
* @init_point: array index of first uninitialized entry
* @first_free: array index of first unused object reference entry
* @last_free: array index of last unused object reference entry
* @index_mask: bitmask for array index portion of reference values
* @start_mask: initial value for instance value portion of reference values
*/
struct ref_table {
struct reference *entries;
u32 capacity;
u32 init_point;
u32 first_free;
u32 last_free;
u32 index_mask;
u32 start_mask;
};
/*
* Object reference table consists of 2**N entries.
*
* State Object ptr Reference
* ----- ---------- ---------
* In use non-NULL XXXX|own index
* (XXXX changes each time entry is acquired)
* Free NULL YYYY|next free index
* (YYYY is one more than last used XXXX)
* Uninitialized NULL 0
*
* Entry 0 is not used; this allows index 0 to denote the end of the free list.
*
* Note that a reference value of 0 does not necessarily indicate that an
* entry is uninitialized, since the last entry in the free list could also
* have a reference value of 0 (although this is unlikely).
*/
static struct ref_table tipc_ref_table;
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 actual_size;
/* account for unused entry, then round up size to a power of 2 */
requested_size++;
for (actual_size = 16; actual_size < requested_size; actual_size <<= 1)
/* do nothing */ ;
/* allocate table & mark all entries as uninitialized */
table = __vmalloc(actual_size * sizeof(struct reference),
GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
if (table == NULL)
return -ENOMEM;
tipc_ref_table.entries = table;
tipc_ref_table.capacity = requested_size;
tipc_ref_table.init_point = 1;
tipc_ref_table.first_free = 0;
tipc_ref_table.last_free = 0;
tipc_ref_table.index_mask = actual_size - 1;
tipc_ref_table.start_mask = start & ~tipc_ref_table.index_mask;
return 0;
}
/**
* 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
*
* Register an object pointer in reference table and lock the object.
* Returns a unique reference value that is used from then on to retrieve the
* object pointer, or to determine that the object has been deregistered.
*
* Note: The object is returned in the locked state so that the caller can
* register a partially initialized object, without running the risk that
* the object will be accessed before initialization is complete.
*/
u32 tipc_ref_acquire(void *object, spinlock_t **lock)
{
u32 index;
u32 index_mask;
u32 next_plus_upper;
u32 ref;
struct reference *entry = NULL;
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;
}
/* take a free entry, if available; otherwise initialize a new entry */
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;
next_plus_upper = entry->ref;
tipc_ref_table.first_free = next_plus_upper & index_mask;
ref = (next_plus_upper & ~index_mask) + index;
} else if (tipc_ref_table.init_point < tipc_ref_table.capacity) {
index = tipc_ref_table.init_point++;
entry = &(tipc_ref_table.entries[index]);
spin_lock_init(&entry->lock);
ref = tipc_ref_table.start_mask + index;
} else {
ref = 0;
}
write_unlock_bh(&ref_table_lock);
/*
* Grab the lock so no one else can modify this entry
* While we assign its ref value & object pointer
*/
if (entry) {
spin_lock_bh(&entry->lock);
entry->ref = ref;
entry->object = object;
*lock = &entry->lock;
/*
* keep it locked, the caller is responsible
* for unlocking this when they're done with it
*/
}
return ref;
}
/**
* 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 (!tipc_ref_table.entries) {
err("Reference table not found during discard attempt\n");
return;
}
index_mask = tipc_ref_table.index_mask;
index = ref & index_mask;
entry = &(tipc_ref_table.entries[index]);
write_lock_bh(&ref_table_lock);
if (!entry->object) {
err("Attempt to discard reference to non-existent object\n");
goto exit;
}
if (entry->ref != ref) {
err("Attempt to discard non-existent reference\n");
goto exit;
}
/*
* mark entry as unused; increment instance part of entry's reference
* to invalidate any subsequent references
*/
entry->object = NULL;
entry->ref = (ref & ~index_mask) + (index_mask + 1);
/* append entry to free entry list */
if (tipc_ref_table.first_free == 0)
tipc_ref_table.first_free = index;
else
tipc_ref_table.entries[tipc_ref_table.last_free].ref |= index;
tipc_ref_table.last_free = index;
exit:
write_unlock_bh(&ref_table_lock);
}
/**
* tipc_ref_lock - lock referenced object and return pointer to it
*/
void *tipc_ref_lock(u32 ref)
{
if (likely(tipc_ref_table.entries)) {
struct reference *entry;
entry = &tipc_ref_table.entries[ref &
tipc_ref_table.index_mask];
if (likely(entry->ref != 0)) {
spin_lock_bh(&entry->lock);
if (likely((entry->ref == ref) && (entry->object)))
return entry->object;
spin_unlock_bh(&entry->lock);
}
}
return NULL;
}
/**
* tipc_ref_deref - return pointer referenced object (without locking it)
*/
void *tipc_ref_deref(u32 ref)
{
if (likely(tipc_ref_table.entries)) {
struct reference *entry;
entry = &tipc_ref_table.entries[ref &
tipc_ref_table.index_mask];
if (likely(entry->ref == ref))
return entry->object;
}
return NULL;
}
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