X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=rculfhash.c;h=600feecfa8f4f8230eede1683cf79cff14a0333f;hp=d89c0cb6635ead96de12a9bdbb82d7c2b8e0a0b2;hb=5f74363e048fb82d7ad97a780eadbeb063840787;hpb=ab65b890d706250367f5b66d86fd0527b57f7b85

diff --git a/rculfhash.c b/rculfhash.c
index d89c0cb..600feec 100644
--- a/rculfhash.c
+++ b/rculfhash.c
@@ -1796,13 +1796,9 @@ void do_resize_cb(struct rcu_head *head)
 }
 
 static
-void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
+void __cds_lfht_resize_lazy_launch(struct cds_lfht *ht)
 {
 	struct rcu_resize_work *work;
-	unsigned long target_size = size << growth;
-
-	if (resize_target_grow(ht, target_size) >= target_size)
-		return;
 
 	/* Store resize_target before read resize_initiated */
 	cmm_smp_mb();
@@ -1820,27 +1816,47 @@ void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int grow
 	}
 }
 
+static
+void cds_lfht_resize_lazy_grow(struct cds_lfht *ht, unsigned long size, int growth)
+{
+	unsigned long target_size = size << growth;
+
+	if (resize_target_grow(ht, target_size) >= target_size)
+		return;
+
+	__cds_lfht_resize_lazy_launch(ht);
+}
+
+/*
+ * We favor grow operations over shrink. A shrink operation never occurs
+ * if a grow operation is queued for lazy execution. A grow operation
+ * cancels any pending shrink lazy execution.
+ */
 static
 void cds_lfht_resize_lazy_count(struct cds_lfht *ht, unsigned long size,
 				unsigned long count)
 {
-	struct rcu_resize_work *work;
-
 	if (!(ht->flags & CDS_LFHT_AUTO_RESIZE))
 		return;
-	resize_target_update_count(ht, count);
-	/* Store resize_target before read resize_initiated */
-	cmm_smp_mb();
-	if (!CMM_LOAD_SHARED(ht->t.resize_initiated)) {
-		uatomic_inc(&ht->in_progress_resize);
-		cmm_smp_mb();	/* increment resize count before load destroy */
-		if (CMM_LOAD_SHARED(ht->in_progress_destroy)) {
-			uatomic_dec(&ht->in_progress_resize);
+	count = max(count, ht->min_alloc_size);
+	if (count == size)
+		return;		/* Already the right size, no resize needed */
+	if (count > size) {	/* lazy grow */
+		if (resize_target_grow(ht, count) >= count)
 			return;
+	} else {		/* lazy shrink */
+		for (;;) {
+			unsigned long s;
+
+			s = uatomic_cmpxchg(&ht->t.resize_target, size, count);
+			if (s == size)
+				break;	/* no resize needed */
+			if (s > size)
+				return;	/* growing is/(was just) in progress */
+			if (s <= count)
+				return;	/* some other thread do shrink */
+			size = s;
 		}
-		work = malloc(sizeof(*work));
-		work->ht = ht;
-		ht->cds_lfht_call_rcu(&work->head, do_resize_cb);
-		CMM_STORE_SHARED(ht->t.resize_initiated, 1);
 	}
+	__cds_lfht_resize_lazy_launch(ht);
 }