X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=2a450459f5cfa50e94bce03e00be0ad1be7b2b4f;hp=b9f795fd1349e6b28e2ac4c1e1f0de57154adad7;hb=7c75d49894833089f34b7e71196e60b2ae5979b1;hpb=5f177b1c042fd3f1b746dee55a90cc503c5276ee

diff --git a/rculfhash.c b/rculfhash.c
index b9f795f..2a45045 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -129,7 +129,7 @@
  *  - cds_lfht_first followed iteration with cds_lfht_next (and/or
  *    cds_lfht_next_duplicate, although less common).
  *
- * We define "write" operations as any of cds_lfht_add,
+ * We define "write" operations as any of cds_lfht_add, cds_lfht_replace,
  * cds_lfht_add_unique (success), cds_lfht_add_replace, cds_lfht_del.
  *
  * When cds_lfht_add_unique succeeds (returns the node passed as
@@ -281,7 +281,7 @@
  * Split-counters lazily update the global counter each 1024
  * addition/removal. It automatically keeps track of resize required.
  * We use the bucket length as indicator for need to expand for small
- * tables and machines lacking per-cpu data suppport.
+ * tables and machines lacking per-cpu data support.
  */
 #define COUNT_COMMIT_ORDER		10
 #define DEFAULT_SPLIT_COUNT_MASK	0xFUL
@@ -381,7 +381,8 @@ uint8_t bit_reverse_u8(uint8_t v)
 	return BitReverseTable256[v];
 }
 
-static __attribute__((unused))
+#if (CAA_BITS_PER_LONG == 32)
+static
 uint32_t bit_reverse_u32(uint32_t v)
 {
 	return ((uint32_t) bit_reverse_u8(v) << 24) | 
@@ -389,8 +390,8 @@ uint32_t bit_reverse_u32(uint32_t v)
 		((uint32_t) bit_reverse_u8(v >> 16) << 8) | 
 		((uint32_t) bit_reverse_u8(v >> 24));
 }
-
-static __attribute__((unused))
+#else
+static
 uint64_t bit_reverse_u64(uint64_t v)
 {
 	return ((uint64_t) bit_reverse_u8(v) << 56) | 
@@ -402,6 +403,7 @@ uint64_t bit_reverse_u64(uint64_t v)
 		((uint64_t) bit_reverse_u8(v >> 48) << 8) |
 		((uint64_t) bit_reverse_u8(v >> 56));
 }
+#endif
 
 static
 unsigned long bit_reverse_ulong(unsigned long v)
@@ -561,6 +563,7 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 
 static long nr_cpus_mask = -1;
 static long split_count_mask = -1;
+static int split_count_order = -1;
 
 #if defined(HAVE_SYSCONF)
 static void ht_init_nr_cpus_mask(void)
@@ -589,20 +592,21 @@ static void ht_init_nr_cpus_mask(void)
 static
 void alloc_split_items_count(struct cds_lfht *ht)
 {
-	struct ht_items_count *count;
-
 	if (nr_cpus_mask == -1)	{
 		ht_init_nr_cpus_mask();
 		if (nr_cpus_mask < 0)
 			split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
 		else
 			split_count_mask = nr_cpus_mask;
+		split_count_order =
+			cds_lfht_get_count_order_ulong(split_count_mask + 1);
 	}
 
 	assert(split_count_mask >= 0);
 
 	if (ht->flags & CDS_LFHT_ACCOUNTING) {
-		ht->split_count = calloc(split_count_mask + 1, sizeof(*count));
+		ht->split_count = calloc(split_count_mask + 1,
+					sizeof(struct ht_items_count));
 		assert(ht->split_count);
 	} else {
 		ht->split_count = NULL;
@@ -712,14 +716,39 @@ void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
 	 * Use bucket-local length for small table expand and for
 	 * environments lacking per-cpu data support.
 	 */
-	if (count >= (1UL << COUNT_COMMIT_ORDER))
+	if (count >= (1UL << (COUNT_COMMIT_ORDER + split_count_order)))
 		return;
 	if (chain_len > 100)
 		dbg_printf("WARNING: large chain length: %u.\n",
 			   chain_len);
-	if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD)
-		cds_lfht_resize_lazy_grow(ht, size,
-			cds_lfht_get_count_order_u32(chain_len - (CHAIN_LEN_TARGET - 1)));
+	if (chain_len >= CHAIN_LEN_RESIZE_THRESHOLD) {
+		int growth;
+
+		/*
+		 * Ideal growth calculated based on chain length.
+		 */
+		growth = cds_lfht_get_count_order_u32(chain_len
+				- (CHAIN_LEN_TARGET - 1));
+		if ((ht->flags & CDS_LFHT_ACCOUNTING)
+				&& (size << growth)
+					>= (1UL << (COUNT_COMMIT_ORDER
+						+ split_count_order))) {
+			/*
+			 * If ideal growth expands the hash table size
+			 * beyond the "small hash table" sizes, use the
+			 * maximum small hash table size to attempt
+			 * expanding the hash table. This only applies
+			 * when node accounting is available, otherwise
+			 * the chain length is used to expand the hash
+			 * table in every case.
+			 */
+			growth = COUNT_COMMIT_ORDER + split_count_order
+				- cds_lfht_get_count_order_ulong(size);
+			if (growth <= 0)
+				return;
+		}
+		cds_lfht_resize_lazy_grow(ht, size, growth);
+	}
 }
 
 static
@@ -734,12 +763,6 @@ int is_removed(struct cds_lfht_node *node)
 	return ((unsigned long) node) & REMOVED_FLAG;
 }
 
-static
-struct cds_lfht_node *flag_removed(struct cds_lfht_node *node)
-{
-	return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG);
-}
-
 static
 int is_bucket(struct cds_lfht_node *node)
 {
@@ -764,6 +787,12 @@ struct cds_lfht_node *flag_removal_owner(struct cds_lfht_node *node)
 	return (struct cds_lfht_node *) (((unsigned long) node) | REMOVAL_OWNER_FLAG);
 }
 
+static
+struct cds_lfht_node *flag_removed_or_removal_owner(struct cds_lfht_node *node)
+{
+	return (struct cds_lfht_node *) (((unsigned long) node) | REMOVED_FLAG | REMOVAL_OWNER_FLAG);
+}
+
 static
 struct cds_lfht_node *get_end(void)
 {
@@ -832,13 +861,16 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *nod
 
 	assert(!is_bucket(bucket));
 	assert(!is_removed(bucket));
+	assert(!is_removal_owner(bucket));
 	assert(!is_bucket(node));
 	assert(!is_removed(node));
+	assert(!is_removal_owner(node));
 	for (;;) {
 		iter_prev = bucket;
 		/* We can always skip the bucket node initially */
 		iter = rcu_dereference(iter_prev->next);
 		assert(!is_removed(iter));
+		assert(!is_removal_owner(iter));
 		assert(iter_prev->reverse_hash <= node->reverse_hash);
 		/*
 		 * We should never be called with bucket (start of chain)
@@ -859,6 +891,7 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *bucket, struct cds_lfht_node *nod
 			iter = next;
 		}
 		assert(!is_removed(iter));
+		assert(!is_removal_owner(iter));
 		if (is_bucket(iter))
 			new_next = flag_bucket(clear_flag(next));
 		else
@@ -879,8 +912,10 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
 		return -ENOENT;
 
 	assert(!is_removed(old_node));
+	assert(!is_removal_owner(old_node));
 	assert(!is_bucket(old_node));
 	assert(!is_removed(new_node));
+	assert(!is_removal_owner(new_node));
 	assert(!is_bucket(new_node));
 	assert(new_node != old_node);
 	for (;;) {
@@ -894,6 +929,12 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
 		}
 		assert(old_next == clear_flag(old_next));
 		assert(new_node != old_next);
+		/*
+		 * REMOVAL_OWNER flag is _NEVER_ set before the REMOVED
+		 * flag. It is either set atomically at the same time
+		 * (replace) or after (del).
+		 */
+		assert(!is_removal_owner(old_next));
 		new_node->next = old_next;
 		/*
 		 * Here is the whole trick for lock-free replace: we add
@@ -906,10 +947,12 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
 		 * the old node, but will not see the new one.
 		 * This is a replacement of a node with another node
 		 * that has the same value: we are therefore not
-		 * removing a value from the hash table.
+		 * removing a value from the hash table. We set both the
+		 * REMOVED and REMOVAL_OWNER flags atomically so we own
+		 * the node after successful cmpxchg.
 		 */
 		ret_next = uatomic_cmpxchg(&old_node->next,
-			      old_next, flag_removed(new_node));
+			old_next, flag_removed_or_removal_owner(new_node));
 		if (ret_next == old_next)
 			break;		/* We performed the replacement. */
 		old_next = ret_next;
@@ -923,7 +966,7 @@ int _cds_lfht_replace(struct cds_lfht *ht, unsigned long size,
 	bucket = lookup_bucket(ht, size, bit_reverse_ulong(old_node->reverse_hash));
 	_cds_lfht_gc_bucket(bucket, new_node);
 
-	assert(is_removed(rcu_dereference(old_node->next)));
+	assert(is_removed(CMM_LOAD_SHARED(old_node->next)));
 	return 0;
 }
 
@@ -947,6 +990,7 @@ void _cds_lfht_add(struct cds_lfht *ht,
 
 	assert(!is_bucket(node));
 	assert(!is_removed(node));
+	assert(!is_removal_owner(node));
 	bucket = lookup_bucket(ht, size, hash);
 	for (;;) {
 		uint32_t chain_len = 0;
@@ -1007,7 +1051,9 @@ void _cds_lfht_add(struct cds_lfht *ht,
 	insert:
 		assert(node != clear_flag(iter));
 		assert(!is_removed(iter_prev));
+		assert(!is_removal_owner(iter_prev));
 		assert(!is_removed(iter));
+		assert(!is_removal_owner(iter));
 		assert(iter_prev != node);
 		if (!bucket_flag)
 			node->next = clear_flag(iter);
@@ -1027,6 +1073,7 @@ void _cds_lfht_add(struct cds_lfht *ht,
 
 	gc_node:
 		assert(!is_removed(iter));
+		assert(!is_removal_owner(iter));
 		if (is_bucket(iter))
 			new_next = flag_bucket(clear_flag(next));
 		else
@@ -1061,10 +1108,15 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
 	 * logical removal flag). Return -ENOENT if the node had
 	 * previously been removed.
 	 */
-	next = rcu_dereference(node->next);
+	next = CMM_LOAD_SHARED(node->next);	/* next is not dereferenced */
 	if (caa_unlikely(is_removed(next)))
 		return -ENOENT;
 	assert(!is_bucket(next));
+	/*
+	 * The del operation semantic guarantees a full memory barrier
+	 * before the uatomic_or atomic commit of the deletion flag.
+	 */
+	cmm_smp_mb__before_uatomic_or();
 	/*
 	 * We set the REMOVED_FLAG unconditionally. Note that there may
 	 * be more than one concurrent thread setting this flag.
@@ -1082,7 +1134,7 @@ int _cds_lfht_del(struct cds_lfht *ht, unsigned long size,
 	bucket = lookup_bucket(ht, size, bit_reverse_ulong(node->reverse_hash));
 	_cds_lfht_gc_bucket(bucket, node);
 
-	assert(is_removed(rcu_dereference(node->next)));
+	assert(is_removed(CMM_LOAD_SHARED(node->next)));
 	/*
 	 * Last phase: atomically exchange node->next with a version
 	 * having "REMOVAL_OWNER_FLAG" set. If the returned node->next
@@ -1137,7 +1189,10 @@ void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
 	}
 	partition_len = len >> cds_lfht_get_count_order_ulong(nr_threads);
 	work = calloc(nr_threads, sizeof(*work));
-	assert(work);
+	if (!work) {
+		dbg_printf("error allocating for resize, single-threading\n");
+		goto fallback;
+	}
 	for (thread = 0; thread < nr_threads; thread++) {
 		work[thread].ht = ht;
 		work[thread].i = i;
@@ -1153,6 +1208,11 @@ void partition_resize_helper(struct cds_lfht *ht, unsigned long i,
 		assert(!ret);
 	}
 	free(work);
+	return;
+fallback:
+	ht->flavor->thread_online();
+	fct(ht, i, 0, len);
+	ht->flavor->thread_offline();
 }
 
 /*
@@ -1510,7 +1570,7 @@ void cds_lfht_lookup(struct cds_lfht *ht, unsigned long hash,
 		}
 		node = clear_flag(next);
 	}
-	assert(!node || !is_bucket(rcu_dereference(node->next)));
+	assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
 	iter->node = node;
 	iter->next = next;
 }
@@ -1543,7 +1603,7 @@ void cds_lfht_next_duplicate(struct cds_lfht *ht, cds_lfht_match_fct match,
 		}
 		node = clear_flag(next);
 	}
-	assert(!node || !is_bucket(rcu_dereference(node->next)));
+	assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
 	iter->node = node;
 	iter->next = next;
 }
@@ -1565,7 +1625,7 @@ void cds_lfht_next(struct cds_lfht *ht, struct cds_lfht_iter *iter)
 		}
 		node = clear_flag(next);
 	}
-	assert(!node || !is_bucket(rcu_dereference(node->next)));
+	assert(!node || !is_bucket(CMM_LOAD_SHARED(node->next)));
 	iter->node = node;
 	iter->next = next;
 }
@@ -1654,12 +1714,14 @@ int cds_lfht_replace(struct cds_lfht *ht,
 
 int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
 {
-	unsigned long size, hash;
+	unsigned long size;
 	int ret;
 
 	size = rcu_dereference(ht->size);
 	ret = _cds_lfht_del(ht, size, node);
 	if (!ret) {
+		unsigned long hash;
+
 		hash = bit_reverse_ulong(node->reverse_hash);
 		ht_count_del(ht, size, hash);
 	}
@@ -1668,7 +1730,7 @@ int cds_lfht_del(struct cds_lfht *ht, struct cds_lfht_node *node)
 
 int cds_lfht_is_node_deleted(struct cds_lfht_node *node)
 {
-	return is_removed(rcu_dereference(node->next));
+	return is_removed(CMM_LOAD_SHARED(node->next));
 }
 
 static
@@ -1684,6 +1746,7 @@ int cds_lfht_delete_bucket(struct cds_lfht *ht)
 		if (!is_bucket(node))
 			return -EPERM;
 		assert(!is_removed(node));
+		assert(!is_removal_owner(node));
 	} while (!is_end(node));
 	/*
 	 * size accessed without rcu_dereference because hash table is
@@ -1710,13 +1773,25 @@ int cds_lfht_delete_bucket(struct cds_lfht *ht)
  */
 int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
 {
-	int ret;
+	int ret, was_online;
 
 	/* Wait for in-flight resize operations to complete */
 	_CMM_STORE_SHARED(ht->in_progress_destroy, 1);
 	cmm_smp_mb();	/* Store destroy before load resize */
+	was_online = ht->flavor->read_ongoing();
+	if (was_online)
+		ht->flavor->thread_offline();
+	/* Calling with RCU read-side held is an error. */
+	if (ht->flavor->read_ongoing()) {
+		ret = -EINVAL;
+		if (was_online)
+			ht->flavor->thread_online();
+		goto end;
+	}
 	while (uatomic_read(&ht->in_progress_resize))
 		poll(NULL, 0, 100);	/* wait for 100ms */
+	if (was_online)
+		ht->flavor->thread_online();
 	ret = cds_lfht_delete_bucket(ht);
 	if (ret)
 		return ret;
@@ -1724,6 +1799,7 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
 	if (attr)
 		*attr = ht->resize_attr;
 	poison_free(ht);
+end:
 	return ret;
 }
 
@@ -1852,13 +1928,30 @@ void resize_target_update_count(struct cds_lfht *ht,
 
 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
 {
+	int was_online;
+
+	was_online = ht->flavor->read_ongoing();
+	if (was_online)
+		ht->flavor->thread_offline();
+	/* Calling with RCU read-side held is an error. */
+	if (ht->flavor->read_ongoing()) {
+		static int print_once;
+
+		if (!CMM_LOAD_SHARED(print_once))
+			fprintf(stderr, "[error] rculfhash: cds_lfht_resize "
+				"called with RCU read-side lock held.\n");
+		CMM_STORE_SHARED(print_once, 1);
+		assert(0);
+		goto end;
+	}
 	resize_target_update_count(ht, new_size);
 	CMM_STORE_SHARED(ht->resize_initiated, 1);
-	ht->flavor->thread_offline();
 	pthread_mutex_lock(&ht->resize_mutex);
 	_do_cds_lfht_resize(ht);
 	pthread_mutex_unlock(&ht->resize_mutex);
-	ht->flavor->thread_online();
+end:
+	if (was_online)
+		ht->flavor->thread_online();
 }
 
 static