X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=6a80049ddd1f783a21e117d63437eec5771ba514;hp=b74739f29a30f1953b3e6447fcf8daa44e069354;hb=53960c9f970e231b1ca5f53913b60d298540cf9a;hpb=dd51e0ad14ab677d0fab45b492150adce2ee863e

diff --git a/rculfhash.c b/rculfhash.c
index b74739f..6a80049 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -120,11 +120,11 @@
  * order              bits       reverse
  * 0               0  000        000
  *                 |
- * 1               |  1  001        100             <-
- *                 |  |                              |
- * 2               |  |  2  010        010           |
- *                 |  |  |  3  011        110    <-  |
- *                 |  |  |  |                     |  |
+ * 1               |  1  001        100       <-    <-
+ *                 |  |                        |     |
+ * 2               |  |  2  010        010     |     |
+ *                 |  |  |  3  011        110  | <-  |
+ *                 |  |  |  |                  |  |  |
  * 3               -> |  |  |  4  100        001  |  |
  *                    -> |  |     5  101        101  |
  *                       -> |        6  110        011
@@ -156,6 +156,9 @@
 #define dbg_printf(fmt, args...)
 #endif
 
+/* For testing */
+#define POISON_FREE
+
 /*
  * Per-CPU split-counters lazily update the global counter each 1024
  * addition/removal. It automatically keeps track of resize required.
@@ -166,6 +169,16 @@
 #define CHAIN_LEN_TARGET		1
 #define CHAIN_LEN_RESIZE_THRESHOLD	3
 
+/*
+ * Define the minimum table size. Protects against hash table resize overload
+ * when too many entries are added quickly before the resize can complete.
+ * This is especially the case if the table could be shrinked to a size of 1.
+ * TODO: we might want to make the add/remove operations help the resize to
+ * add or remove dummy nodes when a resize is ongoing to ensure upper-bound on
+ * chain length.
+ */
+#define MIN_TABLE_SIZE			128
+
 #ifndef max
 #define max(a, b)	((a) > (b) ? (a) : (b))
 #endif
@@ -201,6 +214,7 @@ struct cds_lfht {
 	cds_lfht_hash_fct hash_fct;
 	cds_lfht_compare_fct compare_fct;
 	unsigned long hash_seed;
+	int flags;
 	pthread_mutex_t resize_mutex;	/* resize mutex: add/del mutex */
 	unsigned int in_progress_resize, in_progress_destroy;
 	void (*cds_lfht_call_rcu)(struct rcu_head *head,
@@ -407,6 +421,16 @@ int get_count_order_ulong(unsigned long x)
 	return order;
 }
 
+#ifdef POISON_FREE
+#define poison_free(ptr)				\
+	do {						\
+		memset(ptr, 0x42, sizeof(*(ptr)));	\
+		free(ptr);				\
+	} while (0)
+#else
+#define poison_free(ptr)	free(ptr)
+#endif
+
 static
 void cds_lfht_resize_lazy(struct cds_lfht *ht, struct rcu_table *t, int growth);
 
@@ -457,7 +481,7 @@ struct ht_items_count *alloc_per_cpu_items_count(void)
 static
 void free_per_cpu_items_count(struct ht_items_count *count)
 {
-	free(count);
+	poison_free(count);
 }
 
 static
@@ -567,6 +591,8 @@ void check_resize(struct cds_lfht *ht, struct rcu_table *t,
 {
 	unsigned long count;
 
+	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
+		return;
 	count = uatomic_read(&ht->count);
 	/*
 	 * Use bucket-local length for small table expand and for
@@ -631,7 +657,7 @@ void cds_lfht_free_table_cb(struct rcu_head *head)
 {
 	struct rcu_table *t =
 		caa_container_of(head, struct rcu_table, head);
-	free(t);
+	poison_free(t);
 }
 
 static
@@ -639,7 +665,7 @@ void cds_lfht_free_level(struct rcu_head *head)
 {
 	struct rcu_level *l =
 		caa_container_of(head, struct rcu_level, head);
-	free(l);
+	poison_free(l);
 }
 
 /*
@@ -649,12 +675,28 @@ static
 void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node)
 {
 	struct cds_lfht_node *iter_prev, *iter, *next, *new_next;
-
+	struct cds_lfht_node *iter_trace[64];
+	unsigned long trace_idx = 0;
+
+	memset(iter_trace, 0, sizeof(iter_trace));
+	assert(!is_dummy(dummy));
+	assert(!is_removed(dummy));
+	assert(!is_dummy(node));
+	assert(!is_removed(node));
 	for (;;) {
+		iter_trace[trace_idx++ & (64 - 1)] = (void *) 0x1;
 		iter_prev = dummy;
 		/* We can always skip the dummy node initially */
 		iter = rcu_dereference(iter_prev->p.next);
+		iter_trace[trace_idx++ & (64 - 1)] = iter;
 		assert(iter_prev->p.reverse_hash <= node->p.reverse_hash);
+		/*
+		 * We should never be called with dummy (start of chain)
+		 * and logically removed node (end of path compression
+		 * marker) being the actual same node. This would be a
+		 * bug in the algorithm implementation.
+		 */
+		assert(dummy != node);
 		for (;;) {
 			if (unlikely(!clear_flag(iter)))
 				return;
@@ -665,6 +707,7 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node
 				break;
 			iter_prev = clear_flag(iter);
 			iter = next;
+			iter_trace[trace_idx++ & (64 - 1)] = iter;
 		}
 		assert(!is_removed(iter));
 		if (is_dummy(iter))
@@ -672,6 +715,7 @@ void _cds_lfht_gc_bucket(struct cds_lfht_node *dummy, struct cds_lfht_node *node
 		else
 			new_next = clear_flag(next);
 		(void) uatomic_cmpxchg(&iter_prev->p.next, iter, new_next);
+		iter_trace[trace_idx++ & (64 - 1)] = (void *) 0x2;
 	}
 }
 
@@ -684,6 +728,8 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, struct rcu_table *t,
 	struct _cds_lfht_node *lookup;
 	unsigned long hash, index, order;
 
+	assert(!is_dummy(node));
+	assert(!is_removed(node));
 	if (!t->size) {
 		assert(dummy);
 		node->p.next = flag_dummy(NULL);
@@ -699,14 +745,16 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, struct rcu_table *t,
 		 */
 		index = hash & (t->size - 1);
 		order = get_count_order_ulong(index + 1);
-		lookup = &t->tbl[order]->nodes[index & ((1UL << (order - 1)) - 1)];
+		lookup = &t->tbl[order]->nodes[index & ((!order ? 0 : (1UL << (order - 1))) - 1)];
 		iter_prev = (struct cds_lfht_node *) lookup;
 		/* 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 (;;) {
+			/* TODO: check if removed */
 			if (unlikely(!clear_flag(iter)))
 				goto insert;
+			/* TODO: check if removed */
 			if (likely(clear_flag(iter)->p.reverse_hash > node->p.reverse_hash))
 				goto insert;
 			next = rcu_dereference(clear_flag(iter)->p.next);
@@ -728,6 +776,7 @@ struct cds_lfht_node *_cds_lfht_add(struct cds_lfht *ht, struct rcu_table *t,
 	insert:
 		assert(node != clear_flag(iter));
 		assert(!is_removed(iter_prev));
+		assert(!is_removed(iter));
 		assert(iter_prev != node);
 		if (!dummy)
 			node->p.next = clear_flag(iter);
@@ -755,7 +804,7 @@ gc_end:
 	/* Garbage collect logically removed nodes in the bucket */
 	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order]->nodes[index & ((1UL << (order - 1)) - 1)];
+	lookup = &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;
@@ -771,6 +820,8 @@ int _cds_lfht_remove(struct cds_lfht *ht, struct rcu_table *t,
 	unsigned long hash, index, order;
 
 	/* logically delete the node */
+	assert(!is_dummy(node));
+	assert(!is_removed(node));
 	old = rcu_dereference(node->p.next);
 	do {
 		next = old;
@@ -787,27 +838,16 @@ int _cds_lfht_remove(struct cds_lfht *ht, struct rcu_table *t,
 	/* We performed the (logical) deletion. */
 	flagged = 1;
 
-	if (dummy_removal)
-		node = clear_flag(node);
-
 	/*
 	 * 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.
 	 */
 	hash = bit_reverse_ulong(node->p.reverse_hash);
-	/*
-	 * When removing a dummy node, we need to consider the lower
-	 * order table, so we don't end up looking up the dummy nodes we
-	 * are currently removing.
-	 */
-
-	if (dummy_removal)
-		index = hash & ((t->size == 1) ? 0 : (t->size >> 1) - 1);
-	else
-		index = hash & (t->size - 1);
+	assert(t->size > 0);
+	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order]->nodes[index & ((1UL << (order - 1)) - 1)];
+	lookup = &t->tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1)) - 1))];
 	dummy = (struct cds_lfht_node *) lookup;
 	_cds_lfht_gc_bucket(dummy, node);
 end:
@@ -877,22 +917,26 @@ void fini_table(struct cds_lfht *ht, struct rcu_table *t,
 
 		len = !i ? 1 : 1UL << (i - 1);
 		dbg_printf("fini order %lu len: %lu\n", i, len);
+		/*
+		 * Update table size. Need to shrink this table prior to
+		 * removal so gc lookups use non-logically-removed dummy
+		 * nodes.
+		 */
+		t->size = 1UL << (i - 1);
 		/* Unlink */
 		for (j = 0; j < len; j++) {
-			struct cds_lfht_node *new_node =
+			struct cds_lfht_node *fini_node =
 				(struct cds_lfht_node *) &t->tbl[i]->nodes[j];
 
 			dbg_printf("fini entry: i %lu j %lu hash %lu\n",
 				   i, j, !i ? 0 : (1UL << (i - 1)) + j);
-			new_node->p.reverse_hash =
+			fini_node->p.reverse_hash =
 				bit_reverse_ulong(!i ? 0 : (1UL << (i - 1)) + j);
-			(void) _cds_lfht_remove(ht, t, new_node, 1);
+			(void) _cds_lfht_remove(ht, t, fini_node, 1);
 			if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 				break;
 		}
 		ht->cds_lfht_call_rcu(&t->tbl[i]->head, cds_lfht_free_level);
-		/* Update table size */
-		t->size = (i == 1) ? 0 : 1UL << (i - 2);
 		dbg_printf("fini new size: %lu\n", t->size);
 		if (CMM_LOAD_SHARED(ht->in_progress_destroy))
 			break;
@@ -905,6 +949,7 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 			cds_lfht_compare_fct compare_fct,
 			unsigned long hash_seed,
 			unsigned long init_size,
+			int flags,
 			void (*cds_lfht_call_rcu)(struct rcu_head *head,
 					void (*func)(struct rcu_head *head)),
 			void (*cds_lfht_synchronize_rcu)(void))
@@ -925,10 +970,11 @@ struct cds_lfht *cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	ht->percpu_count = alloc_per_cpu_items_count();
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
-	order = get_count_order_ulong(max(init_size, 1)) + 1;
+	order = get_count_order_ulong(max(init_size, MIN_TABLE_SIZE)) + 1;
 	ht->t = calloc(1, sizeof(struct cds_lfht)
 		       + (order * sizeof(struct rcu_level *)));
 	ht->t->size = 0;
+	ht->flags = flags;
 	pthread_mutex_lock(&ht->resize_mutex);
 	init_table(ht, ht->t, 0, order);
 	pthread_mutex_unlock(&ht->resize_mutex);
@@ -948,9 +994,9 @@ struct cds_lfht_node *cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key
 	t = rcu_dereference(ht->t);
 	index = hash & (t->size - 1);
 	order = get_count_order_ulong(index + 1);
-	lookup = &t->tbl[order]->nodes[index & ((1UL << (order - 1)) - 1)];
+	lookup = &t->tbl[order]->nodes[index & (!order ? 0 : ((1UL << (order - 1))) - 1)];
 	dbg_printf("lookup hash %lu index %lu order %lu aridx %lu\n",
-		   hash, index, order, index & ((1UL << (order - 1)) - 1));
+		   hash, index, order, index & (!order ? 0 : ((1UL << (order - 1)) - 1)));
 	node = (struct cds_lfht_node *) lookup;
 	for (;;) {
 		if (unlikely(!node))
@@ -1075,7 +1121,7 @@ int cds_lfht_delete_dummy(struct cds_lfht *ht)
 				bit_reverse_ulong(t->tbl[order]->nodes[i].reverse_hash));
 			assert(is_dummy(t->tbl[order]->nodes[i].next));
 		}
-		free(t->tbl[order]);
+		poison_free(t->tbl[order]);
 	}
 	return 0;
 }
@@ -1095,9 +1141,9 @@ int cds_lfht_destroy(struct cds_lfht *ht)
 	ret = cds_lfht_delete_dummy(ht);
 	if (ret)
 		return ret;
-	free(ht->t);
+	poison_free(ht->t);
 	free_per_cpu_items_count(ht->percpu_count);
-	free(ht);
+	poison_free(ht);
 	return ret;
 }
 
@@ -1162,7 +1208,7 @@ void _do_cds_lfht_shrink(struct cds_lfht *ht, struct rcu_table *old_t,
 	unsigned long old_order, new_order;
 	struct rcu_table *new_t;
 
-	new_size = max(new_size, 1);
+	new_size = max(new_size, MIN_TABLE_SIZE);
 	old_order = get_count_order_ulong(old_size) + 1;
 	new_order = get_count_order_ulong(new_size) + 1;
 	printf("resize from %lu (order %lu) to %lu (order %lu) buckets\n",
@@ -1173,6 +1219,7 @@ void _do_cds_lfht_shrink(struct cds_lfht *ht, struct rcu_table *old_t,
 	memcpy(&new_t->tbl, &old_t->tbl,
 	       new_order * sizeof(struct rcu_level *));
 	new_t->size = !new_order ? 1 : (1UL << (new_order - 1));
+	assert(new_t->size == new_size);
 	new_t->resize_target = new_t->size;
 	new_t->resize_initiated = 0;
 
@@ -1180,9 +1227,10 @@ void _do_cds_lfht_shrink(struct cds_lfht *ht, struct rcu_table *old_t,
 	rcu_assign_pointer(ht->t, new_t);
 
 	/*
-	 * We need to wait for all reader threads to reach Q.S. (and
+	 * We need to wait for all add operations to reach Q.S. (and
 	 * thus use the new table for lookups) before we can start
-	 * releasing the old dummy nodes.
+	 * releasing the old dummy nodes. Otherwise their lookup will
+	 * return a logically removed node as insert position.
 	 */
 	ht->cds_lfht_synchronize_rcu();
 
@@ -1219,19 +1267,18 @@ unsigned long resize_target_update(struct rcu_table *t,
 }
 
 static
-unsigned long resize_target_update_count(struct rcu_table *t,
-				   unsigned long count)
+void resize_target_update_count(struct rcu_table *t,
+				unsigned long count)
 {
-	count = max(count, 1);
-	return uatomic_set(&t->resize_target, count);
+	count = max(count, MIN_TABLE_SIZE);
+	uatomic_set(&t->resize_target, count);
 }
 
 void cds_lfht_resize(struct cds_lfht *ht, unsigned long new_size)
 {
 	struct rcu_table *t = rcu_dereference(ht->t);
-	unsigned long target_size;
 
-	target_size = resize_target_update_count(t, new_size);
+	resize_target_update_count(t, new_size);
 	CMM_STORE_SHARED(t->resize_initiated, 1);
 	pthread_mutex_lock(&ht->resize_mutex);
 	_do_cds_lfht_resize(ht);
@@ -1248,7 +1295,7 @@ void do_resize_cb(struct rcu_head *head)
 	pthread_mutex_lock(&ht->resize_mutex);
 	_do_cds_lfht_resize(ht);
 	pthread_mutex_unlock(&ht->resize_mutex);
-	free(work);
+	poison_free(work);
 	cmm_smp_mb();	/* finish resize before decrement */
 	uatomic_dec(&ht->in_progress_resize);
 }
@@ -1277,9 +1324,10 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, struct rcu_table *t,
 				unsigned long count)
 {
 	struct rcu_resize_work *work;
-	unsigned long target_size;
 
-	target_size = resize_target_update_count(t, count);
+	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
+		return;
+	resize_target_update_count(t, count);
 	if (!CMM_LOAD_SHARED(t->resize_initiated)) {
 		uatomic_inc(&ht->in_progress_resize);
 		cmm_smp_mb();	/* increment resize count before calling it */