From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Fri, 4 Sep 2015 19:44:23 +0000 (-0400)
Subject: Fix: unpublish stream on close
X-Git-Tag: v2.8.0-rc1~401
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=77f7bd852edcc4f7227792553229c59fd590a447

Fix: unpublish stream on close

Fixes a race where data connection can still add indexes after close,
preventing graceful teardown of the stream.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---

diff --git a/src/bin/lttng-relayd/main.c b/src/bin/lttng-relayd/main.c
index 7b385b49f..fe52702c7 100644
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -1266,9 +1266,17 @@ static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
 		ret = -1;
 		goto end;
 	}
+
+	/*
+	 * Set last_net_seq_num before the close flag. Required by data
+	 * pending check.
+	 */
 	pthread_mutex_lock(&stream->lock);
-	stream->closed = true;
 	stream->last_net_seq_num = be64toh(stream_info.last_net_seq_num);
+	pthread_mutex_unlock(&stream->lock);
+
+	stream_close(stream);
+
 	if (stream->is_metadata) {
 		struct relay_viewer_stream *vstream;
 
@@ -1287,7 +1295,6 @@ static int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
 			viewer_stream_put(vstream);
 		}
 	}
-	pthread_mutex_unlock(&stream->lock);
 	stream_put(stream);
 
 end:
diff --git a/src/bin/lttng-relayd/stream.c b/src/bin/lttng-relayd/stream.c
index a314eb9f9..1d1975902 100644
--- a/src/bin/lttng-relayd/stream.c
+++ b/src/bin/lttng-relayd/stream.c
@@ -168,6 +168,7 @@ struct relay_stream *stream_create(struct ctf_trace *trace,
 	 * side of the relayd does not have the concept of session.
 	 */
 	lttng_ht_add_unique_u64(relay_streams_ht, &stream->node);
+	stream->in_stream_ht = true;
 
 	DBG("Relay new stream added %s with ID %" PRIu64, stream->channel_name,
 			stream->stream_handle);
@@ -225,20 +226,27 @@ unlock:
 }
 
 /*
- * Only called from destroy. No stream lock needed, since there is a
- * single user at this point. This is ensured by having the refcount
- * reaching 0.
+ * Stream must be protected by holding the stream lock or by virtue of being
+ * called from stream_destroy, in which case it is guaranteed to be accessed
+ * from a single thread by the reflock.
  */
 static void stream_unpublish(struct relay_stream *stream)
 {
-	if (!stream->published) {
-		return;
+	if (stream->in_stream_ht) {
+		struct lttng_ht_iter iter;
+		int ret;
+
+		iter.iter.node = &stream->node.node;
+		ret = lttng_ht_del(relay_streams_ht, &iter);
+		assert(!ret);
+		stream->in_stream_ht = false;
+	}
+	if (stream->published) {
+		pthread_mutex_lock(&stream->trace->stream_list_lock);
+		cds_list_del_rcu(&stream->stream_node);
+		pthread_mutex_unlock(&stream->trace->stream_list_lock);
+		stream->published = false;
 	}
-	pthread_mutex_lock(&stream->trace->stream_list_lock);
-	cds_list_del_rcu(&stream->stream_node);
-	pthread_mutex_unlock(&stream->trace->stream_list_lock);
-
-	stream->published = false;
 }
 
 static void stream_destroy(struct relay_stream *stream)
@@ -274,8 +282,6 @@ static void stream_release(struct urcu_ref *ref)
 	struct relay_stream *stream =
 		caa_container_of(ref, struct relay_stream, ref);
 	struct relay_session *session;
-	int ret;
-	struct lttng_ht_iter iter;
 
 	session = stream->trace->session;
 
@@ -289,10 +295,6 @@ static void stream_release(struct urcu_ref *ref)
 	}
 	pthread_mutex_unlock(&session->recv_list_lock);
 
-	iter.iter.node = &stream->node.node;
-	ret = lttng_ht_del(relay_streams_ht, &iter);
-	assert(!ret);
-
 	stream_unpublish(stream);
 
 	if (stream->stream_fd) {
@@ -340,6 +342,7 @@ void stream_close(struct relay_stream *stream)
 {
 	DBG("closing stream %" PRIu64, stream->stream_handle);
 	pthread_mutex_lock(&stream->lock);
+	stream_unpublish(stream);
 	stream->closed = true;
 	relay_index_close_all(stream);
 	pthread_mutex_unlock(&stream->lock);
diff --git a/src/bin/lttng-relayd/stream.h b/src/bin/lttng-relayd/stream.h
index ca6be8133..542e05c0f 100644
--- a/src/bin/lttng-relayd/stream.h
+++ b/src/bin/lttng-relayd/stream.h
@@ -132,6 +132,7 @@ struct relay_stream {
 	 * Node of stream within global stream hash table.
 	 */
 	struct lttng_ht_node_u64 node;
+	bool in_stream_ht;		/* is stream in stream hash table. */
 	struct rcu_head rcu_node;	/* For call_rcu teardown. */
 };