X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-registry.c;h=399d48f681d8e0aa22bd269109e580f0e2206d77;hb=020d7f606b4264ec26bdae8b84d6e85182539ab2;hp=b538a8fa9f37d6f5108c609a3021a27173cbe9ac;hpb=9209cee7e4ccdb6c8c14047a4727bac41302a632;p=lttng-tools.git

diff --git a/src/bin/lttng-sessiond/ust-registry.c b/src/bin/lttng-sessiond/ust-registry.c
index b538a8fa9..399d48f68 100644
--- a/src/bin/lttng-sessiond/ust-registry.c
+++ b/src/bin/lttng-sessiond/ust-registry.c
@@ -308,12 +308,28 @@ void ust_registry_destroy_event(struct ust_registry_channel *chan,
 	return;
 }
 
+/*
+ * We need to execute ht_destroy outside of RCU read-side critical
+ * section, so we postpone its execution using call_rcu. It is simpler
+ * than to change the semantic of the many callers of
+ * destroy_channel().
+ */
+static
+void destroy_channel_rcu(struct rcu_head *head)
+{
+	struct ust_registry_channel *chan =
+		caa_container_of(head, struct ust_registry_channel, rcu_head);
+
+	if (chan->ht) {
+		lttng_ht_destroy(chan->ht);
+	}
+	free(chan);
+}
+
 /*
  * Destroy every element of the registry and free the memory. This does NOT
  * free the registry pointer since it might not have been allocated before so
  * it's the caller responsability.
- *
- * This *MUST NOT* be called within a RCU read side lock section.
  */
 static void destroy_channel(struct ust_registry_channel *chan)
 {
@@ -329,9 +345,7 @@ static void destroy_channel(struct ust_registry_channel *chan)
 		ust_registry_destroy_event(chan, event);
 	}
 	rcu_read_unlock();
-
-	lttng_ht_destroy(chan->ht);
-	free(chan);
+	call_rcu(&chan->rcu_head, destroy_channel_rcu);
 }
 
 /*
@@ -349,7 +363,7 @@ int ust_registry_channel_add(struct ust_registry_session *session,
 	if (!chan) {
 		PERROR("zmalloc ust registry channel");
 		ret = -ENOMEM;
-		goto error;
+		goto error_alloc;
 	}
 
 	chan->ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
@@ -378,7 +392,11 @@ int ust_registry_channel_add(struct ust_registry_session *session,
 	lttng_ht_add_unique_u64(session->channels, &chan->node);
 	rcu_read_unlock();
 
+	return 0;
+
 error:
+	destroy_channel(chan);
+error_alloc:
 	return ret;
 }
 
@@ -435,12 +453,6 @@ void ust_registry_channel_del_free(struct ust_registry_session *session,
 	ret = lttng_ht_del(session->channels, &iter);
 	assert(!ret);
 	rcu_read_unlock();
-
-	/*
-	 * Destroying the hash table should be done without RCU
-	 * read-side lock held. Since we own "chan" now, it is OK to use
-	 * it outside of RCU read-side critical section.
-	 */
 	destroy_channel(chan);
 
 end:
@@ -474,7 +486,7 @@ int ust_registry_session_init(struct ust_registry_session **sessionp,
 	session = zmalloc(sizeof(*session));
 	if (!session) {
 		PERROR("zmalloc ust registry session");
-		goto error;
+		goto error_alloc;
 	}
 
 	pthread_mutex_init(&session->lock, NULL);
@@ -510,6 +522,8 @@ int ust_registry_session_init(struct ust_registry_session **sessionp,
 	return 0;
 
 error:
+	ust_registry_session_destroy(session);
+error_alloc:
 	return -1;
 }
 
@@ -535,8 +549,10 @@ void ust_registry_session_destroy(struct ust_registry_session *reg)
 		assert(!ret);
 		destroy_channel(chan);
 	}
-	lttng_ht_destroy(reg->channels);
 	rcu_read_unlock();
 
+	if (reg->channels) {
+		lttng_ht_destroy(reg->channels);
+	}
 	free(reg->metadata);
 }