/*
* The removed flag needs to be updated atomically with the pointer.
+ * It indicates that no node must attach to the node scheduled for
+ * removal. The gc flag also needs to be updated atomically with the
+ * pointer. It indicates that node garbage collection must be performed.
* The dummy flag does not require to be updated atomically with the
* pointer, but it is added as a pointer low bit flag to save space.
*/
#define REMOVED_FLAG (1UL << 0)
-#define DUMMY_FLAG (1UL << 1)
-#define FLAGS_MASK ((1UL << 2) - 1)
+#define GC_FLAG (1UL << 1)
+#define DUMMY_FLAG (1UL << 2)
+#define FLAGS_MASK ((1UL << 3) - 1)
/* Value of the end pointer. Should not interact with flags. */
#define END_VALUE NULL
unsigned long start, unsigned long len);
};
+enum add_mode {
+ ADD_DEFAULT = 0,
+ ADD_UNIQUE = 1,
+ ADD_REPLACE = 2,
+};
+
static
struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
unsigned long size,
struct cds_lfht_node *node,
- int unique, int dummy);
+ enum add_mode mode, int dummy);
+
+static
+int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
+ struct cds_lfht_node *node,
+ int dummy_removal, int do_gc);
/*
* Algorithm to reverse bits in a word by lookup table, extended to
return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG);
}
+static
+int is_gc(struct cds_lfht_node *node)
+{
+ return ((unsigned long) node) & GC_FLAG;
+}
+
+static
+struct cds_lfht_node *flag_gc(struct cds_lfht_node *node)
+{
+ return (struct cds_lfht_node *) (((unsigned long) node) | GC_FLAG);
+}
+
static
int is_dummy(struct cds_lfht_node *node)
{
struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
assert(!is_dummy(dummy));
+ assert(!is_gc(dummy));
assert(!is_removed(dummy));
assert(!is_dummy(node));
+ assert(!is_gc(node));
assert(!is_removed(node));
for (;;) {
iter_prev = dummy;
if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
return;
next = rcu_dereference(clear_flag(iter)->p.next);
- if (likely(is_removed(next)))
+ if (likely(is_gc(next)))
break;
iter_prev = clear_flag(iter);
iter = next;
}
- assert(!is_removed(iter));
+ assert(!is_gc(iter));
if (is_dummy(iter))
new_next = flag_dummy(clear_flag(next));
else
new_next = clear_flag(next);
+ if (is_removed(iter))
+ new_next = flag_removed(new_next);
(void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
}
return;
struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht,
unsigned long size,
struct cds_lfht_node *node,
- int unique, int dummy)
+ enum add_mode mode, int dummy)
{
struct cds_lfht_node *iter_prev, *iter, *next, *new_node, *new_next,
- *dummy_node;
+ *dummy_node, *return_node;
struct _cds_lfht_node *lookup;
unsigned long hash, index, order;
assert(!is_dummy(node));
+ assert(!is_gc(node));
assert(!is_removed(node));
if (!size) {
assert(dummy);
if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
goto insert;
next = rcu_dereference(clear_flag(iter)->p.next);
- if (unlikely(is_removed(next)))
+ if (unlikely(is_gc(next)))
goto gc_node;
- if (unique
+ assert(!is_removed(next));
+ if ((mode == ADD_UNIQUE || mode == ADD_REPLACE)
&& !is_dummy(next)
&& !ht->compare_fct(node->key, node->key_len,
clear_flag(iter)->key,
- clear_flag(iter)->key_len))
- return clear_flag(iter);
+ clear_flag(iter)->key_len)) {
+ if (mode == ADD_UNIQUE)
+ return clear_flag(iter);
+ else /* mode == ADD_REPLACE */
+ goto replace;
+ }
/* Only account for identical reverse hash once */
if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash
&& !is_dummy(next))
iter_prev = clear_flag(iter);
iter = next;
}
+
insert:
assert(node != clear_flag(iter));
assert(!is_removed(iter_prev));
assert(!is_removed(iter));
+ assert(!is_gc(iter_prev));
+ assert(!is_gc(iter));
assert(iter_prev != node);
if (!dummy)
node->p.next = clear_flag(iter);
else
new_node = node;
if (uatomic_cmpxchg(&iter_prev->p.next, iter,
- new_node) != iter)
+ new_node) != iter) {
continue; /* retry */
+ } else {
+ if (mode == ADD_REPLACE)
+ return_node = NULL;
+ else /* ADD_DEFAULT and ADD_UNIQUE */
+ return_node = node;
+ goto gc_end;
+ }
+
+ replace:
+ /* Insert after node to be replaced */
+ iter_prev = clear_flag(iter);
+ iter = next;
+ assert(node != clear_flag(iter));
+ assert(!is_removed(iter_prev));
+ assert(!is_removed(iter));
+ assert(!is_gc(iter_prev));
+ assert(!is_gc(iter));
+ assert(iter_prev != node);
+ assert(!dummy);
+ node->p.next = clear_flag(iter);
+ if (is_dummy(iter))
+ new_node = flag_dummy(node);
else
+ new_node = node;
+ /*
+ * Here is the whole trick for lock-free replace: we add
+ * the replacement node _after_ the node we want to
+ * replace by atomically setting its next pointer at the
+ * same time we set its removal and gc flags. Given that
+ * the lookups/get next use an iterator aware of the
+ * next pointer, they will either skip the old node due
+ * to the removal/gc flag and see the new node, or use
+ * the old new, but will not see the new one.
+ */
+ new_node = flag_removed(new_node);
+ new_node = flag_gc(new_node);
+ if (uatomic_cmpxchg(&iter_prev->p.next,
+ iter, new_node) != iter) {
+ continue; /* retry */
+ } else {
+ return_node = iter_prev;
goto gc_end;
+ }
+
gc_node:
assert(!is_removed(iter));
+ assert(!is_gc(iter));
if (is_dummy(iter))
new_next = flag_dummy(clear_flag(next));
else
lookup = &ht->t.tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
dummy_node = (struct cds_lfht_node *) lookup;
_cds_lfht_gc_bucket(dummy_node, node);
- return node;
+ return return_node;
}
static
int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
struct cds_lfht_node *node,
- int dummy_removal)
+ int dummy_removal, int do_gc)
{
struct cds_lfht_node *dummy, *next, *old;
struct _cds_lfht_node *lookup;
/* logically delete the node */
assert(!is_dummy(node));
+ assert(!is_gc(node));
assert(!is_removed(node));
old = rcu_dereference(node->p.next);
do {
+ struct cds_lfht_node *new_next;
+
next = old;
if (unlikely(is_removed(next)))
goto end;
assert(is_dummy(next));
else
assert(!is_dummy(next));
- old = uatomic_cmpxchg(&node->p.next, next,
- flag_removed(next));
+ new_next = flag_removed(next);
+ if (do_gc)
+ new_next = flag_gc(new_next);
+ old = uatomic_cmpxchg(&node->p.next, next, new_next);
} while (old != next);
/* We performed the (logical) deletion. */
flagged = 1;
+ if (!do_gc)
+ goto end;
+
/*
* Ensure that the node is not visible to readers anymore: lookup for
* the node, and remove it (along with any other logically removed node)
new_node->p.reverse_hash =
bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
(void) _cds_lfht_add(ht, !i ? 0 : (1UL << (i - 1)),
- new_node, 0, 1);
+ new_node, ADD_DEFAULT, 1);
if (CMM_LOAD_SHARED(ht->in_progress_destroy))
break;
}
fini_node->p.reverse_hash =
bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
(void) _cds_lfht_del(ht, !i ? 0 : (1UL << (i - 1)),
- fini_node, 1);
+ fini_node, 1, 1);
if (CMM_LOAD_SHARED(ht->in_progress_destroy))
break;
}
return ht;
}
-struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len)
+void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
+ struct cds_lfht_iter *iter)
{
struct cds_lfht_node *node, *next, *dummy_node;
struct _cds_lfht_node *lookup;
node = clear_flag(next);
}
assert(!node || !is_dummy(rcu_dereference(node->p.next)));
- return node;
+ iter->node = node;
+ iter->next = next;
}
-struct cds_lfht_node *cds_lfht_next(struct cds_lfht *ht,
- struct cds_lfht_node *node)
+void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
{
- struct cds_lfht_node *next;
+ struct cds_lfht_node *node, *next;
unsigned long reverse_hash;
void *key;
size_t key_len;
+ node = iter->node;
reverse_hash = node->p.reverse_hash;
key = node->key;
key_len = node->key_len;
- next = rcu_dereference(node->p.next);
+ next = iter->next;
node = clear_flag(next);
for (;;) {
node = clear_flag(next);
}
assert(!node || !is_dummy(rcu_dereference(node->p.next)));
- return node;
+ iter->node = node;
+ iter->next = next;
}
void cds_lfht_add(struct cds_lfht *ht, struct cds_lfht_node *node)
node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
size = rcu_dereference(ht->t.size);
- (void) _cds_lfht_add(ht, size, node, 0, 0);
+ (void) _cds_lfht_add(ht, size, node, ADD_DEFAULT, 0);
ht_count_add(ht, size);
}
struct cds_lfht_node *cds_lfht_add_unique(struct cds_lfht *ht,
- struct cds_lfht_node *node)
+ struct cds_lfht_node *node)
{
unsigned long hash, size;
struct cds_lfht_node *ret;
node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
size = rcu_dereference(ht->t.size);
- ret = _cds_lfht_add(ht, size, node, 1, 0);
+ ret = _cds_lfht_add(ht, size, node, ADD_UNIQUE, 0);
if (ret == node)
ht_count_add(ht, size);
return ret;
}
+struct cds_lfht_node *cds_lfht_replace(struct cds_lfht *ht,
+ struct cds_lfht_node *node)
+{
+ unsigned long hash, size;
+ struct cds_lfht_node *ret;
+
+ hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+ node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
+
+ size = rcu_dereference(ht->t.size);
+ ret = _cds_lfht_add(ht, size, node, ADD_REPLACE, 0);
+ if (ret == NULL)
+ ht_count_add(ht, size);
+ return ret;
+}
+
int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
{
unsigned long size;
int ret;
size = rcu_dereference(ht->t.size);
- ret = _cds_lfht_del(ht, size, node, 0);
+ ret = _cds_lfht_del(ht, size, node, 0, 1);
if (!ret)
ht_count_del(ht, size);
return ret;
if (!is_dummy(node))
return -EPERM;
assert(!is_removed(node));
+ assert(!is_gc(node));
} while (!is_end(node));
/*
* size accessed without rcu_dereference because hash table is
node = (struct cds_lfht_node *) lookup;
do {
next = rcu_dereference(node->p.next);
- if (is_removed(next)) {
+ if (is_removed(next) || is_gc(next)) {
assert(!is_dummy(next));
(*removed)++;
} else if (!is_dummy(next))
projects / urcu.git / blobdiff