X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=0c433e54050ea0ba311b91114f6c58b26222629e;hp=a3223f37f046021cb6c3c0119e107e2e4dde4fd0;hb=b453eae1adf45ba2377e50c15b438c77c96a35b5;hpb=848d408839fe4f829db477644c776eba166a0e9a

diff --git a/rculfhash.c b/rculfhash.c
index a3223f3..0c433e5 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -53,6 +53,15 @@
 #define max(a, b)	((a) > (b) ? (a) : (b))
 #endif
 
+/*
+ * The removed flag needs to be updated atomically with the pointer.
+ * 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)
+
 struct rcu_table {
 	unsigned long size;	/* always a power of 2 */
 	unsigned long resize_target;
@@ -176,21 +185,33 @@ void check_resize(struct rcu_ht *ht, struct rcu_table *t,
 static
 struct rcu_ht_node *clear_flag(struct rcu_ht_node *node)
 {
-	return (struct rcu_ht_node *) (((unsigned long) node) & ~0x1);
+	return (struct rcu_ht_node *) (((unsigned long) node) & ~FLAGS_MASK);
 }
 
 static
 int is_removed(struct rcu_ht_node *node)
 {
-	return ((unsigned long) node) & 0x1;
+	return ((unsigned long) node) & REMOVED_FLAG;
 }
 
 static
 struct rcu_ht_node *flag_removed(struct rcu_ht_node *node)
 {
-	return (struct rcu_ht_node *) (((unsigned long) node) | 0x1);
+	return (struct rcu_ht_node *) (((unsigned long) node) | REMOVED_FLAG);
 }
 
+static
+int is_dummy(struct rcu_ht_node *node)
+{
+	return ((unsigned long) node) & DUMMY_FLAG;
+}
+
+static
+struct rcu_ht_node *flag_dummy(struct rcu_ht_node *node)
+{
+	return (struct rcu_ht_node *) (((unsigned long) node) | DUMMY_FLAG);
+}
+ 
 static
 unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 {
@@ -211,41 +232,47 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 static
 void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
 {
-	struct rcu_ht_node *iter_prev, *iter, *next;
+	struct rcu_ht_node *iter_prev, *iter, *next, *new_next;
 
 	for (;;) {
 		iter_prev = dummy;
 		/* We can always skip the dummy node initially */
-		iter = rcu_dereference(iter_prev->next);
-		assert(iter_prev->reverse_hash <= node->reverse_hash);
+		iter = rcu_dereference(iter_prev->p.next);
+		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
 		for (;;) {
-			if (unlikely(!iter))
+			if (unlikely(!clear_flag(iter)))
 				return;
-			if (clear_flag(iter)->reverse_hash > node->reverse_hash)
+			if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)
 				return;
-			next = rcu_dereference(clear_flag(iter)->next);
+			next = rcu_dereference(clear_flag(iter)->p.next);
 			if (is_removed(next))
 				break;
-			iter_prev = iter;
+			iter_prev = clear_flag(iter);
 			iter = next;
 		}
 		assert(!is_removed(iter));
-		(void) uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next));
+		if (is_dummy(iter))
+			new_next = flag_dummy(clear_flag(next));
+		else
+			new_next = clear_flag(next);
+		(void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
 	}
 }
 
 static
 struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
-			    struct rcu_ht_node *node, int unique)
+			    struct rcu_ht_node *node, int unique, int dummy)
 {
-	struct rcu_ht_node *iter_prev, *dummy, *iter, *next;
+	struct rcu_ht_node *iter_prev, *iter, *next, *new_node, *new_next,
+			*dummy_node;
 	unsigned long hash;
 
 	if (!t->size) {
-		assert(node->dummy);
+		assert(dummy);
+		node->p.next = flag_dummy(NULL);
 		return node;	/* Initial first add (head) */
 	}
-	hash = bit_reverse_ulong(node->reverse_hash);
+	hash = bit_reverse_ulong(node->p.reverse_hash);
 	for (;;) {
 		uint32_t chain_len = 0;
 
@@ -255,24 +282,24 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
 		 */
 		iter_prev = rcu_dereference(t->tbl[hash & (t->size - 1)]);
 		/* We can always skip the dummy node initially */
-		iter = rcu_dereference(iter_prev->next);
-		assert(iter_prev->reverse_hash <= node->reverse_hash);
+		iter = rcu_dereference(iter_prev->p.next);
+		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
 		for (;;) {
-			if (unlikely(!iter))
+			if (unlikely(!clear_flag(iter)))
 				goto insert;
-			if (clear_flag(iter)->reverse_hash > node->reverse_hash)
+			if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)
 				goto insert;
-			next = rcu_dereference(clear_flag(iter)->next);
+			next = rcu_dereference(clear_flag(iter)->p.next);
 			if (is_removed(next))
 				goto gc_node;
 			if (unique
-			    && !clear_flag(iter)->dummy
+			    && !is_dummy(next)
 			    && !ht->compare_fct(node->key, node->key_len,
 						clear_flag(iter)->key,
 						clear_flag(iter)->key_len))
 				return clear_flag(iter);
 			/* Only account for identical reverse hash once */
-			if (iter_prev->reverse_hash != clear_flag(iter)->reverse_hash)
+			if (iter_prev->p.reverse_hash != clear_flag(iter)->p.reverse_hash)
 				check_resize(ht, t, ++chain_len);
 			iter_prev = clear_flag(iter);
 			iter = next;
@@ -281,21 +308,32 @@ struct rcu_ht_node *_ht_add(struct rcu_ht *ht, struct rcu_table *t,
 		assert(node != clear_flag(iter));
 		assert(!is_removed(iter_prev));
 		assert(iter_prev != node);
-		node->next = iter;
-		if (uatomic_cmpxchg(&iter_prev->next, iter,
-				    node) != iter)
+		if (!dummy)
+			node->p.next = clear_flag(iter);
+		else
+			node->p.next = flag_dummy(clear_flag(iter));
+		if (is_dummy(iter))
+			new_node = flag_dummy(node);
+		else
+			new_node = node;
+		if (uatomic_cmpxchg(&iter_prev->p.next, iter,
+				    new_node) != iter)
 			continue;	/* retry */
 		else
 			goto gc_end;
 	gc_node:
 		assert(!is_removed(iter));
-		(void) uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next));
+		if (is_dummy(iter))
+			new_next = flag_dummy(clear_flag(next));
+		else
+			new_next = clear_flag(next);
+		(void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
 		/* retry */
 	}
 gc_end:
 	/* Garbage collect logically removed nodes in the bucket */
-	dummy = rcu_dereference(t->tbl[hash & (t->size - 1)]);
-	_ht_gc_bucket(dummy, node);
+	dummy_node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+	_ht_gc_bucket(dummy_node, node);
 	return node;
 }
 
@@ -307,13 +345,13 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 	unsigned long hash;
 
 	/* logically delete the node */
-	old = rcu_dereference(node->next);
+	old = rcu_dereference(node->p.next);
 	do {
 		next = old;
 		if (is_removed(next))
 			goto end;
-		assert(!node->dummy);
-		old = uatomic_cmpxchg(&node->next, next,
+		assert(!is_dummy(next));
+		old = uatomic_cmpxchg(&node->p.next, next,
 				      flag_removed(next));
 	} while (old != next);
 
@@ -325,7 +363,7 @@ int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 	 * the node, and remove it (along with any other logically removed node)
 	 * if found.
 	 */
-	hash = bit_reverse_ulong(node->reverse_hash);
+	hash = bit_reverse_ulong(node->p.reverse_hash);
 	dummy = rcu_dereference(t->tbl[hash & (t->size - 1)]);
 	_ht_gc_bucket(dummy, node);
 end:
@@ -334,7 +372,7 @@ end:
 	 * removed the node from the hash.
 	 */
 	if (flagged) {
-		assert(is_removed(rcu_dereference(node->next)));
+		assert(is_removed(rcu_dereference(node->p.next)));
 		return 0;
 	} else
 		return -ENOENT;
@@ -351,10 +389,9 @@ void init_table(struct rcu_ht *ht, struct rcu_table *t,
 		/* Update table size when power of two */
 		if (i != 0 && !(i & (i - 1)))
 			t->size = i;
-		t->tbl[i] = calloc(1, sizeof(struct rcu_ht_node));
-		t->tbl[i]->dummy = 1;
-		t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
-		(void) _ht_add(ht, t, t->tbl[i], 0);
+		t->tbl[i] = calloc(1, sizeof(struct _rcu_ht_node));
+		t->tbl[i]->p.reverse_hash = bit_reverse_ulong(i);
+		(void) _ht_add(ht, t, t->tbl[i], 0, 1);
 	}
 	t->resize_target = t->size = end;
 	t->resize_initiated = 0;
@@ -389,7 +426,7 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 {
 	struct rcu_table *t;
-	struct rcu_ht_node *node;
+	struct rcu_ht_node *node, *next;
 	unsigned long hash, reverse_hash;
 
 	hash = ht->hash_fct(key, key_len, ht->hash_seed);
@@ -400,18 +437,19 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 	for (;;) {
 		if (unlikely(!node))
 			break;
-		if (unlikely(node->reverse_hash > reverse_hash)) {
+		if (unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = NULL;
 			break;
 		}
-		if (likely(!is_removed(rcu_dereference(node->next)))
-		    && !node->dummy
+		next = rcu_dereference(node->p.next);
+		if (likely(!is_removed(next))
+		    && !is_dummy(next)
 		    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
 				break;
 		}
-		node = clear_flag(rcu_dereference(node->next));
+		node = clear_flag(next);
 	}
-	assert(!node || !node->dummy);
+	assert(!node || !is_dummy(rcu_dereference(node->p.next)));
 	return node;
 }
 
@@ -421,10 +459,10 @@ void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
 	unsigned long hash;
 
 	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
-	node->reverse_hash = bit_reverse_ulong((unsigned long) hash);
+	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	t = rcu_dereference(ht->t);
-	(void) _ht_add(ht, t, node, 0);
+	(void) _ht_add(ht, t, node, 0, 0);
 }
 
 struct rcu_ht_node *ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
@@ -433,10 +471,10 @@ struct rcu_ht_node *ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
 	unsigned long hash;
 
 	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
-	node->reverse_hash = bit_reverse_ulong((unsigned long) hash);
+	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	t = rcu_dereference(ht->t);
-	return _ht_add(ht, t, node, 1);
+	return _ht_add(ht, t, node, 1, 0);
 }
 
 int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
@@ -458,14 +496,14 @@ int ht_delete_dummy(struct rcu_ht *ht)
 	/* Check that the table is empty */
 	node = t->tbl[0];
 	do {
-		if (!node->dummy)
+		node = clear_flag(node)->p.next;
+		if (!is_dummy(node))
 			return -EPERM;
-		node = node->next;
 		assert(!is_removed(node));
-	} while (node);
+	} while (clear_flag(node));
 	/* Internal sanity check: all nodes left should be dummy */
 	for (i = 0; i < t->size; i++) {
-		assert(t->tbl[i]->dummy);
+		assert(is_dummy(t->tbl[i]->p.next));
 		free(t->tbl[i]);
 	}
 	return 0;
@@ -504,11 +542,11 @@ void ht_count_nodes(struct rcu_ht *ht,
 	/* Check that the table is empty */
 	node = rcu_dereference(t->tbl[0]);
 	do {
-		next = rcu_dereference(node->next);
+		next = rcu_dereference(node->p.next);
 		if (is_removed(next)) {
-			assert(!node->dummy);
+			assert(!is_dummy(next));
 			(*removed)++;
-		} else if (!node->dummy)
+		} else if (!is_dummy(next))
 			(*count)++;
 		node = clear_flag(next);
 	} while (node);