int l_remove(node_t *head, key_t key) {
node_t *pred, *item, *sitem;
while (TRUE) {
if (!l_find(&pred, &item, head, key)) {
trace("remove item failed %d\n", key);
return FALSE;
}
sitem = STRIP_MARK(item);
node_t *inext = sitem->next;
/* 先标记再删除 */
if (!CAS(&sitem->next, inext, MARK(inext))) {
trace("cas item %p mark failed\n", sitem->next);
continue;
}
sitem->val = NULL_VALUE;
int tag = GET_TAG(pred->next) + 1;
if (CAS(&pred->next, item, TAG(STRIP_MARK(sitem->next), tag))) {
trace("remove item %p success\n", item);
haz_defer_free(sitem);
return TRUE;
}
trace("cas item remove item %p failed\n", item);
}
return FALSE;
}
value_t l_lookup(node_t *head, key_t key) {
node_t *pred, *item;
if (l_find(&pred, &item, head, key)) {
return STRIP_MARK(item)->val;
}
return NULL_VALUE;
}
int l_find(node_t **pred_ptr, node_t **item_ptr, node_t *head, key_t key) {
node_t *pred = head;
node_t *item = head->next;
/* pred和next会被使用，所以进行标记 */
hazard_t *hp1 = haz_get(0);
hazard_t *hp2 = haz_get(1);
while (item) {
node_t *sitem = STRIP_MARK(item);
haz_set_ptr(hp1, STRIP_MARK(pred));
haz_set_ptr(hp2, STRIP_MARK(item));
/*
如果已被标记，那么紧接着item可能被移除链表甚至释放，所以需要重头查找
*/
if (HAS_MARK(sitem->next)) {
trace("item->next %p %p marked, retry\n", item, sitem->next);
return l_find(pred_ptr, item_ptr, head, key);
}
int d = KEY_CMP(sitem->key, key);
if (d >= 0) {
trace("item %p match key %d, pred %p\n", item, key, pred);
*pred_ptr = pred;
*item_ptr = item;
return d == 0 ? TRUE : FALSE;
}
pred = item;
item = sitem->next;
}
trace("not found key %d\n", key);
*pred_ptr = pred;
*item_ptr = NULL;
return FALSE;
}
/*
DESCRIPTION
deletes a node as identified by hashnr/keey/keylen from the list
that starts from 'head'
RETURN
0 - ok
1 - not found
NOTE
it uses pins[0..2], on return all pins are removed.
*/
static int l_delete(LF_SLIST * volatile *head, CHARSET_INFO *cs, uint32 hashnr,
const uchar *key, uint keylen, LF_PINS *pins)
{
CURSOR cursor;
int res;
for (;;)
{
if (!l_find(head, cs, hashnr, key, keylen, &cursor, pins))
{
res= 1; /* not found */
break;
}
else
{
/* mark the node deleted */
if (my_atomic_casptr((void **) (char*) &(cursor.curr->link),
(void **) (char*) &cursor.next,
(void *)(((intptr)cursor.next) | 1)))
{
/* and remove it from the list */
if (my_atomic_casptr((void **)cursor.prev,
(void **)(char*)&cursor.curr, cursor.next))
_lf_alloc_free(pins, cursor.curr);
else
{
/*
somebody already "helped" us and removed the node ?
Let's check if we need to help that someone too!
(to ensure the number of "set DELETED flag" actions
is equal to the number of "remove from the list" actions)
*/
l_find(head, cs, hashnr, key, keylen, &cursor, pins);
}
res= 0;
break;
}
}
}
_lf_unpin(pins, 0);
_lf_unpin(pins, 1);
_lf_unpin(pins, 2);
return res;
}
/*
Test the find function.
*/
void find_test(linked_list list, int item, int result) {
link l = l_find(list, item);
if (l == NULL && result != 0) {
printf("Find test failed: expected to find %d, got NULL.\n", item);
}
else if (l != NULL && result == 0) {
printf("Find test failed: expected NULL when finding %d.\n", item);
}
else if (l != NULL && l->item != item) {
printf("Find test failed: expected %d, found %d.\n", item, l->item);
}
}
/*
DESCRIPTION
searches for a node as identified by hashnr/keey/keylen in the list
that starts from 'head'
RETURN
0 - not found
node - found
NOTE
it uses pins[0..2], on return the pin[2] keeps the node found
all other pins are removed.
*/
static LF_SLIST *l_search(LF_SLIST * volatile *head, CHARSET_INFO *cs,
uint32 hashnr, const uchar *key, uint keylen,
LF_PINS *pins)
{
CURSOR cursor;
int res= l_find(head, cs, hashnr, key, keylen, &cursor, pins);
if (res)
_lf_pin(pins, 2, cursor.curr);
else
_lf_unpin(pins, 2);
_lf_unpin(pins, 1);
_lf_unpin(pins, 0);
return res ? cursor.curr : 0;
}
static int add_section_label(struct label *l, const char *name,
const char *attribute, uint64_t value,
struct label **length)
{
char label[255];
int errcode;
errcode = create_section_label_name(label, sizeof(label), name,
attribute);
if (errcode < 0)
return errcode;
errcode = l_append(l, label, value);
if (errcode < 0)
return errcode;
if (length)
*length = l_find(l, label);
return 0;
}
/**
Iterate over all elements in hash and call function with the element
@note
If one of 'action' invocations returns 1 the iteration aborts.
'action' might see some elements twice!
@retval 0 ok
@retval 1 error (action returned 1)
*/
int lf_hash_iterate(LF_HASH *hash, LF_PINS *pins,
my_hash_walk_action action, void *argument)
{
CURSOR cursor;
uint bucket= 0;
int res;
LF_SLIST * volatile *el;
el= lf_dynarray_lvalue(&hash->array, bucket);
if (unlikely(!el))
return 0; /* if there's no bucket==0, the hash is empty */
if (*el == NULL && unlikely(initialize_bucket(hash, el, bucket, pins)))
return 0; /* if there's no bucket==0, the hash is empty */
res= l_find(el, 0, 0, (uchar*)argument, 0, &cursor, pins, action);
lf_unpin(pins, 2);
lf_unpin(pins, 1);
lf_unpin(pins, 0);
return res;
}
/*
DESCRIPTION
insert a 'node' in the list that starts from 'head' in the correct
position (as found by l_find)
RETURN
0 - inserted
not 0 - a pointer to a duplicate (not pinned and thus unusable)
NOTE
it uses pins[0..2], on return all pins are removed.
if there're nodes with the same key value, a new node is added before them.
*/
static LF_SLIST *l_insert(LF_SLIST * volatile *head, CHARSET_INFO *cs,
LF_SLIST *node, LF_PINS *pins, uint flags)
{
CURSOR cursor;
int res;
for (;;)
{
if (l_find(head, cs, node->hashnr, node->key, node->keylen,
&cursor, pins) &&
(flags & LF_HASH_UNIQUE))
{
res= 0; /* duplicate found */
break;
}
else
{
node->link= (intptr)cursor.curr;
DBUG_ASSERT(node->link != (intptr)node); /* no circular references */
DBUG_ASSERT(cursor.prev != &node->link); /* no circular references */
if (my_atomic_casptr((void **) cursor.prev,
(void **)(char*) &cursor.curr, node))
{
res= 1; /* inserted ok */
break;
}
}
}
_lf_unpin(pins, 0);
_lf_unpin(pins, 1);
_lf_unpin(pins, 2);
/*
Note that cursor.curr is not pinned here and the pointer is unreliable,
the object may dissapear anytime. But if it points to a dummy node, the
pointer is safe, because dummy nodes are never freed - initialize_bucket()
uses this fact.
*/
return res ? 0 : cursor.curr;
}
value_t l_insert(node_t *head, key_t key, value_t val) {
node_t *pred, *item, *new_item;
while (TRUE) {
if (l_find(&pred, &item, head, key)) { /* update its value */
/* 更新值时，使用item->val互斥，NULL_VALUE表示被删除 */
node_t *sitem = STRIP_MARK(item);
value_t old_val = sitem->val;
while (old_val != NULL_VALUE) {
value_t ret = CAS_V(&sitem->val, old_val, val);
if (ret == old_val) {
trace("update item %p value success\n", item);
return ret;
}
trace("update item lost race %p\n", item);
old_val = ret;
}
trace("item %p removed, retry\n", item);
continue; /* the item has been removed, we retry */
}
new_item = (node_t*) malloc(sizeof(node_t));
new_item->key = key;
new_item->val = val;
new_item->next = item;
/* a). pred是否有效问题：无效只会发生在使用pred->next时，而l_remove正移除该pred
就会在CAS(&item->next)中竞争，如果remove中成功，那么insert CAS就失败，
然后重试；反之，remove失败重试，所以保证了pred有效
b). item本身增加tag一定程度上降低ABA问题几率
*/
if (CAS(&pred->next, item, new_item)) {
trace("insert item %p(next) %p success\n", item, new_item);
return val;
}
trace("cas item %p failed, retry\n", item);
free(new_item);
}
return NULL_VALUE;
}
void big_test() {
linked_list list = l_create();
l_add_front(list, 3);
length_test(list, 1);
front_test(list, 3);
back_test(list, 3);
//list = 3
l_add_back(list, 4);
length_test(list, 2);
front_test(list, 3);
back_test(list, 4);
//list = 3, 4
l_add_front(list, 2);
length_test(list, 3);
front_test(list, 2);
back_test(list, 4);
//list = 2, 3, 4
int array1[] = {2, 3, 4};
print_test(list, array1, 3);
l_add_front(list, 1);
l_add_back(list, 5);
length_test(list, 5);
front_test(list, 1);
back_test(list, 5);
//list = 1, 2, 3, 4, 5
find_test(list, 3, 1);
link l = l_find(list, 3);
l_remove(list, l);
find_test(list, 3, 0);
length_test(list, 4);
front_test(list, 1);
back_test(list, 5);
//list = 1, 2, 4, 5
int array2[] = {1, 2, 4, 5};
print_test(list, array2, 4);
l_remove_back(list);
length_test(list, 3);
back_test(list, 4);
//list = 1, 2, 4
l_remove_front(list);
length_test(list, 2);
front_test(list, 2);
//list = 2, 4
l_destroy(list);
}
int l_exist(node_t *head, key_t key) {
node_t *pred, *item;
return l_find(&pred, &item, head, key);
}