X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=55f56ceb6bc54a248032d3e2ce94e2db1bfeb82b;hp=497a9eacdebd764771d1e6e2e88a95c019f83724;hb=1b81fe1a14149b4c3f878b53e050a6ad5374a569;hpb=732ad076c182b3ad706cd62f8a6694f921e1bb7c

diff --git a/rculfhash.c b/rculfhash.c
index 497a9ea..55f56ce 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -46,15 +46,21 @@
 #define dbg_printf(args...)
 #endif
 
-#define BUCKET_SIZE_RESIZE_THRESHOLD	4
+#define CHAIN_LEN_TARGET		1
+#define CHAIN_LEN_RESIZE_THRESHOLD	2
 
 #ifndef max
 #define max(a, b)	((a) > (b) ? (a) : (b))
 #endif
 
+#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;
+	int resize_initiated;
 	struct rcu_head head;
 	struct rcu_ht_node *tbl[0];
 };
@@ -65,6 +71,7 @@ struct rcu_ht {
 	ht_compare_fct compare_fct;
 	unsigned long hash_seed;
 	pthread_mutex_t resize_mutex;	/* resize mutex: add/del mutex */
+	unsigned int in_progress_resize;
 	void (*ht_call_rcu)(struct rcu_head *head,
 		      void (*func)(struct rcu_head *head));
 };
@@ -165,28 +172,41 @@ static
 void check_resize(struct rcu_ht *ht, struct rcu_table *t,
 		  uint32_t chain_len)
 {
-	if (chain_len >= BUCKET_SIZE_RESIZE_THRESHOLD)
-		ht_resize_lazy(ht, t, log2_u32(chain_len));
+	if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
+		ht_resize_lazy(ht, t,
+			log2_u32(chain_len - CHAIN_LEN_TARGET - 1));
 }
 
 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)
 {
@@ -201,97 +221,156 @@ unsigned long _uatomic_max(unsigned long *ptr, unsigned long v)
 	return v;
 }
 
+/*
+ * Remove all logically deleted nodes from a bucket up to a certain node key.
+ */
 static
-void _ht_add(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
+void _ht_gc_bucket(struct rcu_ht_node *dummy, struct rcu_ht_node *node)
 {
-	struct rcu_ht_node *iter_prev = NULL, *iter = NULL;
+	struct rcu_ht_node *iter_prev, *iter, *next, *new_next;
 
-	if (!t->size)
-		return;
 	for (;;) {
-		uint32_t chain_len = 0;
-
-		iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
-		assert(iter_prev);
-		assert(iter_prev->reverse_hash <= node->reverse_hash);
+		iter_prev = dummy;
+		/* We can always skip the dummy node initially */
+		iter = rcu_dereference(iter_prev->p.next);
+		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
 		for (;;) {
-			iter = clear_flag(rcu_dereference(iter_prev->next));
-			if (unlikely(!iter))
-				break;
-			if (iter->reverse_hash < node->reverse_hash)
+			if (unlikely(!clear_flag(iter)))
+				return;
+			if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)
+				return;
+			next = rcu_dereference(clear_flag(iter)->p.next);
+			if (is_removed(next))
 				break;
 			iter_prev = iter;
-			check_resize(ht, t, ++chain_len);
+			iter = next;
 		}
-		/* add in iter_prev->next */
-		if (is_removed(iter))
-			continue;
-		assert(node != iter);
-		node->next = iter;
+		assert(!is_removed(iter));
+		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, int dummy)
+{
+	struct rcu_ht_node *iter_prev, *iter, *next, *new_node, *new_next,
+			*dummy_node;
+	unsigned long hash;
+
+	if (!t->size) {
+		assert(dummy);
+		node->p.next = flag_dummy(NULL);
+		return node;	/* Initial first add (head) */
+	}
+	hash = bit_reverse_ulong(node->p.reverse_hash);
+	for (;;) {
+		uint32_t chain_len = 0;
+
+		/*
+		 * iter_prev points to the non-removed node prior to the
+		 * insert location.
+		 */
+		iter_prev = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+		/* We can always skip the dummy node initially */
+		iter = rcu_dereference(iter_prev->p.next);
+		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
+		for (;;) {
+			if (unlikely(!clear_flag(iter)))
+				goto insert;
+			if (clear_flag(iter)->p.reverse_hash > node->p.reverse_hash)
+				goto insert;
+			next = rcu_dereference(clear_flag(iter)->p.next);
+			if (is_removed(next))
+				goto gc_node;
+			if (unique
+			    && !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->p.reverse_hash != clear_flag(iter)->p.reverse_hash)
+				check_resize(ht, t, ++chain_len);
+			iter_prev = clear_flag(iter);
+			iter = next;
+		}
+	insert:
+		assert(node != clear_flag(iter));
+		assert(!is_removed(iter_prev));
 		assert(iter_prev != node);
-		if (uatomic_cmpxchg(&iter_prev->next, iter, node) != iter)
-			continue;
-		break;
+		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));
+		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_node = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+	_ht_gc_bucket(dummy_node, node);
+	return node;
 }
 
 static
 int _ht_remove(struct rcu_ht *ht, struct rcu_table *t, struct rcu_ht_node *node)
 {
-	struct rcu_ht_node *iter_prev, *iter, *next, *old;
-	unsigned long chain_len;
-	int found, ret = 0;
+	struct rcu_ht_node *dummy, *next, *old;
 	int flagged = 0;
+	unsigned long hash;
 
-retry:
-	chain_len = 0;
-	found = 0;
-	iter_prev = rcu_dereference(t->tbl[node->hash & (t->size - 1)]);
-	assert(iter_prev);
-	assert(iter_prev->reverse_hash <= node->reverse_hash);
-	for (;;) {
-		iter = clear_flag(rcu_dereference(iter_prev->next));
-		if (unlikely(!iter))
-			break;
-		if (iter->reverse_hash < node->reverse_hash)
-			break;
-		if (iter == node) {
-			found = 1;
-			break;
-		}
-		iter_prev = iter;
-	} 
-	if (!found) {
-		ret = -ENOENT;
-		goto end;
-	}
-	next = rcu_dereference(iter->next);
-	if (!flagged) {
-		if (is_removed(next)) {
-			ret = -ENOENT;
+	/* logically delete the node */
+	old = rcu_dereference(node->p.next);
+	do {
+		next = old;
+		if (is_removed(next))
 			goto end;
-		}
-		/* set deletion flag */
-		if ((old = uatomic_cmpxchg(&iter->next, next,
-					   flag_removed(next))) != next) {
-			if (old == flag_removed(next)) {
-				ret = -ENOENT;
-				goto end;
-			} else {
-				goto retry;
-			}
-		}
-		flagged = 1;
-	}
+		assert(!is_dummy(next));
+		old = uatomic_cmpxchg(&node->p.next, next,
+				      flag_removed(next));
+	} while (old != next);
+
+	/* We performed the (logical) deletion. */
+	flagged = 1;
+
 	/*
-	 * Remove the element from the list. Retry if there has been a
-	 * concurrent add (there cannot be a concurrent delete, because
-	 * we won the deletion flag cmpxchg).
+	 * Ensure that the node is not visible to readers anymore: lookup for
+	 * the node, and remove it (along with any other logically removed node)
+	 * if found.
 	 */
-	if (uatomic_cmpxchg(&iter_prev->next, iter, clear_flag(next)) != iter)
-		goto retry;
+	hash = bit_reverse_ulong(node->p.reverse_hash);
+	dummy = rcu_dereference(t->tbl[hash & (t->size - 1)]);
+	_ht_gc_bucket(dummy, node);
 end:
-	return ret;
+	/*
+	 * Only the flagging action indicated that we (and no other)
+	 * removed the node from the hash.
+	 */
+	if (flagged) {
+		assert(is_removed(rcu_dereference(node->p.next)));
+		return 0;
+	} else
+		return -ENOENT;
 }
 
 static
@@ -305,13 +384,12 @@ 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]->hash = i;
-		t->tbl[i]->reverse_hash = bit_reverse_ulong(i);
-		_ht_add(ht, t, t->tbl[i]);
+		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;
 }
 
 struct rcu_ht *ht_new(ht_hash_fct hash_fct,
@@ -328,6 +406,7 @@ struct rcu_ht *ht_new(ht_hash_fct hash_fct,
 	ht->compare_fct = compare_fct;
 	ht->hash_seed = hash_seed;
 	ht->ht_call_rcu = ht_call_rcu;
+	ht->in_progress_resize = 0;
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
 	ht->t = calloc(1, sizeof(struct rcu_table)
@@ -342,7 +421,7 @@ 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);
@@ -353,29 +432,44 @@ struct rcu_ht_node *ht_lookup(struct rcu_ht *ht, void *key, size_t key_len)
 	for (;;) {
 		if (unlikely(!node))
 			break;
-		if (node->reverse_hash > reverse_hash) {
+		if (unlikely(node->p.reverse_hash > reverse_hash)) {
 			node = NULL;
 			break;
 		}
-		if (!ht->compare_fct(node->key, node->key_len, key, key_len)) {
-			if (is_removed(rcu_dereference(node->next)))
-				node = NULL;
-			break;
+		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 || !is_dummy(rcu_dereference(node->p.next)));
 	return node;
 }
 
 void ht_add(struct rcu_ht *ht, struct rcu_ht_node *node)
 {
 	struct rcu_table *t;
+	unsigned long hash;
+
+	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
+
+	t = rcu_dereference(ht->t);
+	(void) _ht_add(ht, t, node, 0, 0);
+}
+
+struct rcu_ht_node *ht_add_unique(struct rcu_ht *ht, struct rcu_ht_node *node)
+{
+	struct rcu_table *t;
+	unsigned long hash;
 
-	node->hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
-	node->reverse_hash = bit_reverse_ulong((unsigned long) node->hash);
+	hash = ht->hash_fct(node->key, node->key_len, ht->hash_seed);
+	node->p.reverse_hash = bit_reverse_ulong((unsigned long) hash);
 
 	t = rcu_dereference(ht->t);
-	_ht_add(ht, t, node);
+	return _ht_add(ht, t, node, 1, 0);
 }
 
 int ht_remove(struct rcu_ht *ht, struct rcu_ht_node *node)
@@ -397,13 +491,14 @@ 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;
-	} while (node);
+		assert(!is_removed(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;
@@ -417,6 +512,9 @@ int ht_destroy(struct rcu_ht *ht)
 {
 	int ret;
 
+	/* Wait for in-flight resize operations to complete */
+	while (uatomic_read(&ht->in_progress_resize))
+		poll(NULL, 0, 100);	/* wait for 100ms */
 	ret = ht_delete_dummy(ht);
 	if (ret)
 		return ret;
@@ -425,6 +523,30 @@ int ht_destroy(struct rcu_ht *ht)
 	return ret;
 }
 
+void ht_count_nodes(struct rcu_ht *ht,
+		unsigned long *count,
+		unsigned long *removed)
+{
+	struct rcu_table *t;
+	struct rcu_ht_node *node, *next;
+
+	*count = 0;
+	*removed = 0;
+
+	t = rcu_dereference(ht->t);
+	/* Check that the table is empty */
+	node = rcu_dereference(t->tbl[0]);
+	do {
+		next = rcu_dereference(node->p.next);
+		if (is_removed(next)) {
+			assert(!is_dummy(next));
+			(*removed)++;
+		} else if (!is_dummy(next))
+			(*count)++;
+		node = clear_flag(next);
+	} while (node);
+}
+
 static
 void ht_free_table_cb(struct rcu_head *head)
 {
@@ -474,6 +596,7 @@ void ht_resize(struct rcu_ht *ht, int growth)
 
 	target_size = resize_target_update(t, growth);
 	if (t->size < target_size) {
+		CMM_STORE_SHARED(t->resize_initiated, 1);
 		pthread_mutex_lock(&ht->resize_mutex);
 		_do_ht_resize(ht);
 		pthread_mutex_unlock(&ht->resize_mutex);
@@ -491,6 +614,8 @@ void do_resize_cb(struct rcu_head *head)
 	_do_ht_resize(ht);
 	pthread_mutex_unlock(&ht->resize_mutex);
 	free(work);
+	cmm_smp_mb();	/* finish resize before decrement */
+	uatomic_dec(&ht->in_progress_resize);
 }
 
 static
@@ -500,9 +625,12 @@ void ht_resize_lazy(struct rcu_ht *ht, struct rcu_table *t, int growth)
 	unsigned long target_size;
 
 	target_size = resize_target_update(t, growth);
-	if (t->size < target_size) {
+	if (!CMM_LOAD_SHARED(t->resize_initiated) && t->size < target_size) {
+		uatomic_inc(&ht->in_progress_resize);
+		cmm_smp_mb();	/* increment resize count before calling it */
 		work = malloc(sizeof(*work));
 		work->ht = ht;
 		ht->ht_call_rcu(&work->head, do_resize_cb);
+		CMM_STORE_SHARED(t->resize_initiated, 1);
 	}
 }