X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=rculfhash.c;h=f4187e7993ca9ea53a6915ede1edb6673388db48;hb=7f52427be704778d53f85e17fb71629b50ada827;hp=46513dfd40562bb7c1e0bb24f39fee3656e378a2;hpb=14360f1c5d88854a94caa9e6a933c430b38731f4;p=urcu.git

diff --git a/rculfhash.c b/rculfhash.c
index 46513df..f4187e7 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -179,6 +179,7 @@
  * tables and machines lacking per-cpu data suppport.
  */
 #define COUNT_COMMIT_ORDER		10
+#define DEFAULT_SPLIT_COUNT_MASK	0xFUL
 #define CHAIN_LEN_TARGET		1
 #define CHAIN_LEN_RESIZE_THRESHOLD	3
 
@@ -221,15 +222,37 @@
 /* Value of the end pointer. Should not interact with flags. */
 #define END_VALUE		NULL
 
+/*
+ * ht_items_count: Split-counters counting the number of node addition
+ * and removal in the table. Only used if the CDS_LFHT_ACCOUNTING flag
+ * is set at hash table creation.
+ *
+ * These are free-running counters, never reset to zero. They count the
+ * number of add/remove, and trigger every (1 << COUNT_COMMIT_ORDER)
+ * operations to update the global counter. We choose a power-of-2 value
+ * for the trigger to deal with 32 or 64-bit overflow of the counter.
+ */
 struct ht_items_count {
 	unsigned long add, del;
 } __attribute__((aligned(CAA_CACHE_LINE_SIZE)));
 
+/*
+ * rcu_level: Contains the per order-index-level dummy node table. The
+ * size of each dummy node table is half the number of hashes contained
+ * in this order (except for order 0). The minimum allocation size
+ * parameter allows combining the dummy node arrays of the lowermost
+ * levels to improve cache locality for small index orders.
+ */
 struct rcu_level {
 	/* Note: manually update allocation length when adding a field */
 	struct _cds_lfht_node nodes[0];
 };
 
+/*
+ * rcu_table: Contains the size and desired new size if a resize
+ * operation is in progress, as well as the statically-sized array of
+ * rcu_level pointers.
+ */
 struct rcu_table {
 	unsigned long size;	/* always a power of 2, shared (RCU) */
 	unsigned long resize_target;
@@ -237,6 +260,11 @@ struct rcu_table {
 	struct rcu_level *tbl[MAX_TABLE_ORDER];
 };
 
+/*
+ * cds_lfht: Top-level data structure representing a lock-free hash
+ * table. Defined in the implementation file to make it be an opaque
+ * cookie to users.
+ */
 struct cds_lfht {
 	struct rcu_table t;
 	cds_lfht_hash_fct hash_fct;
@@ -268,11 +296,20 @@ struct cds_lfht {
 	struct ht_items_count *split_count;	/* split item count */
 };
 
+/*
+ * rcu_resize_work: Contains arguments passed to RCU worker thread
+ * responsible for performing lazy resize.
+ */
 struct rcu_resize_work {
 	struct rcu_head head;
 	struct cds_lfht *ht;
 };
 
+/*
+ * partition_resize_work: Contains arguments passed to worker threads
+ * executing the hash table resize on partitions of the hash table
+ * assigned to each processor's worker thread.
+ */
 struct partition_resize_work {
 	pthread_t thread_id;
 	struct cds_lfht *ht;
@@ -453,7 +490,7 @@ unsigned int fls_u32(uint32_t x)
 
 unsigned int fls_ulong(unsigned long x)
 {
-#if (CAA_BITS_PER_lONG == 32)
+#if (CAA_BITS_PER_LONG == 32)
 	return fls_u32(x);
 #else
 	return fls_u64(x);
@@ -485,10 +522,12 @@ int get_count_order_ulong(unsigned long x)
 }
 
 #ifdef POISON_FREE
-#define poison_free(ptr)				\
-	do {						\
-		memset(ptr, 0x42, sizeof(*(ptr)));	\
-		free(ptr);				\
+#define poison_free(ptr)					\
+	do {							\
+		if (ptr) {					\
+			memset(ptr, 0x42, sizeof(*(ptr)));	\
+			free(ptr);				\
+		}						\
 	} while (0)
 #else
 #define poison_free(ptr)	free(ptr)
@@ -497,14 +536,6 @@ int get_count_order_ulong(unsigned long x)
 static
 void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth);
 
-/*
- * If the sched_getcpu() and sysconf(_SC_NPROCESSORS_CONF) calls are
- * available, then we support hash table item accounting.
- * In the unfortunate event the number of CPUs reported would be
- * inaccurate, we use modulo arithmetic on the number of CPUs we got.
- */
-#if defined(HAVE_SYSCONF)
-
 static
 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 				unsigned long count);
@@ -512,6 +543,7 @@ 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;
 
+#if defined(HAVE_SYSCONF)
 static void ht_init_nr_cpus_mask(void)
 {
 	long maxcpus;
@@ -528,27 +560,40 @@ static void ht_init_nr_cpus_mask(void)
 	maxcpus = 1UL << get_count_order_ulong(maxcpus);
 	nr_cpus_mask = maxcpus - 1;
 }
+#else /* #if defined(HAVE_SYSCONF) */
+static void ht_init_nr_cpus_mask(void)
+{
+	nr_cpus_mask = -2;
+}
+#endif /* #else #if defined(HAVE_SYSCONF) */
 
 static
-struct ht_items_count *alloc_split_items_count(void)
+void alloc_split_items_count(struct cds_lfht *ht)
 {
 	struct ht_items_count *count;
 
 	if (nr_cpus_mask == -1)	{
 		ht_init_nr_cpus_mask();
-		split_count_mask = nr_cpus_mask;
+		if (nr_cpus_mask < 0)
+			split_count_mask = DEFAULT_SPLIT_COUNT_MASK;
+		else
+			split_count_mask = nr_cpus_mask;
 	}
 
-	if (split_count_mask < 0)
-		return NULL;
-	else
-		return calloc(split_count_mask + 1, sizeof(*count));
+	assert(split_count_mask >= 0);
+
+	if (ht->flags & CDS_LFHT_ACCOUNTING) {
+		ht->split_count = calloc(split_count_mask + 1, sizeof(*count));
+		assert(ht->split_count);
+	} else {
+		ht->split_count = NULL;
+	}
 }
 
 static
-void free_split_items_count(struct ht_items_count *count)
+void free_split_items_count(struct cds_lfht *ht)
 {
-	poison_free(count);
+	poison_free(ht->split_count);
 }
 
 #if defined(HAVE_SCHED_GETCPU)
@@ -632,35 +677,6 @@ void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
 	}
 }
 
-#else /* #if defined(HAVE_SYSCONF) */
-
-static const long nr_cpus_mask = -2;
-static const long split_count_mask = -2;
-
-static
-struct ht_items_count *alloc_split_items_count(void)
-{
-	return NULL;
-}
-
-static
-void free_split_items_count(struct ht_items_count *count)
-{
-}
-
-static
-void ht_count_add(struct cds_lfht *ht, unsigned long size, unsigned long hash)
-{
-}
-
-static
-void ht_count_del(struct cds_lfht *ht, unsigned long size, unsigned long hash)
-{
-}
-
-#endif /* #else #if defined(HAVE_SYSCONF) */
-
-
 static
 void check_resize(struct cds_lfht *ht, unsigned long size, uint32_t chain_len)
 {
@@ -1350,6 +1366,7 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	init_size = max(init_size, min_alloc_size);
 	ht = calloc(1, sizeof(struct cds_lfht));
 	assert(ht);
+	ht->flags = flags;
 	ht->hash_fct = hash_fct;
 	ht->compare_fct = compare_fct;
 	ht->hash_seed = hash_seed;
@@ -1362,16 +1379,15 @@ struct cds_lfht *_cds_lfht_new(cds_lfht_hash_fct hash_fct,
 	ht->cds_lfht_rcu_register_thread = cds_lfht_rcu_register_thread;
 	ht->cds_lfht_rcu_unregister_thread = cds_lfht_rcu_unregister_thread;
 	ht->resize_attr = attr;
-	ht->split_count = alloc_split_items_count();
+	alloc_split_items_count(ht);
 	/* this mutex should not nest in read-side C.S. */
 	pthread_mutex_init(&ht->resize_mutex, NULL);
-	ht->flags = flags;
 	order = get_count_order_ulong(init_size);
 	ht->t.resize_target = 1UL << order;
-	cds_lfht_create_dummy(ht, 1UL << order);
-	ht->t.size = 1UL << order;
 	ht->min_alloc_size = min_alloc_size;
 	ht->min_alloc_order = get_count_order_ulong(min_alloc_size);
+	cds_lfht_create_dummy(ht, 1UL << order);
+	ht->t.size = 1UL << order;
 	return ht;
 }
 
@@ -1401,9 +1417,10 @@ void cds_lfht_lookup(struct cds_lfht *ht, void *key, size_t key_len,
 			break;
 		}
 		next = rcu_dereference(node->p.next);
+		assert(node == clear_flag(node));
 		if (likely(!is_removed(next))
 		    && !is_dummy(next)
-		    && clear_flag(node)->p.reverse_hash == reverse_hash
+		    && node->p.reverse_hash == reverse_hash
 		    && likely(!ht->compare_fct(node->key, node->key_len, key, key_len))) {
 				break;
 		}
@@ -1617,7 +1634,7 @@ int cds_lfht_destroy(struct cds_lfht *ht, pthread_attr_t **attr)
 	ret = cds_lfht_delete_dummy(ht);
 	if (ret)
 		return ret;
-	free_split_items_count(ht->split_count);
+	free_split_items_count(ht);
 	if (attr)
 		*attr = ht->resize_attr;
 	poison_free(ht);
@@ -1635,7 +1652,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
 	unsigned long nr_dummy = 0;
 
 	*approx_before = 0;
-	if (split_count_mask >= 0) {
+	if (ht->split_count) {
 		int i;
 
 		for (i = 0; i < split_count_mask + 1; i++) {
@@ -1665,7 +1682,7 @@ void cds_lfht_count_nodes(struct cds_lfht *ht,
 	} while (!is_end(node));
 	dbg_printf("number of dummy nodes: %lu\n", nr_dummy);
 	*approx_after = 0;
-	if (split_count_mask >= 0) {
+	if (ht->split_count) {
 		int i;
 
 		for (i = 0; i < split_count_mask + 1; i++) {
@@ -1802,8 +1819,6 @@ void cds_lfht_resize_lazy(struct cds_lfht *ht, unsigned long size, int growth)
 	}
 }
 
-#if defined(HAVE_SYSCONF)
-
 static
 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 				unsigned long count)
@@ -1828,5 +1843,3 @@ void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 		CMM_STORE_SHARED(ht->t.resize_initiated, 1);
 	}
 }
-
-#endif