From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Fri, 9 Aug 2019 15:18:47 +0000 (-0400)
Subject: relayd fix: trace chunk is reclaimed before close command
X-Git-Tag: v2.11.0-rc3~78
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=a57bb1b0809f64ee342883598f92555158ceca22;p=lttng-tools.git

relayd fix: trace chunk is reclaimed before close command

The relay daemon control protocol defines a trace chunk close command
which allows the tracer to express the 'end' time bound of a trace
chunk.

However, in the event of a session rotation, the last reference to
such a trace chunk can be released before the close command is
received. This prevents the trace chunk from being renamed and moved
at the completion of a rotation.

A reference to a 'pending closure' trace chunk is kept as part of the
relay session object until its 'close' command is received.

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 82e260354..a3e2509d2 100644
--- a/src/bin/lttng-relayd/main.c
+++ b/src/bin/lttng-relayd/main.c
@@ -2423,11 +2423,22 @@ static int relay_create_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
 	}
 
 	pthread_mutex_lock(&conn->session->lock);
-	lttng_trace_chunk_put(conn->session->current_trace_chunk);
+	if (conn->session->pending_closure_trace_chunk) {
+		/*
+		 * Invalid; this means a second create_trace_chunk command was
+		 * received before a close_trace_chunk.
+		 */
+		ERR("Invalid trace chunk close command received; a trace chunk is already waiting for a trace chunk close command");
+		reply_code = LTTNG_ERR_INVALID_PROTOCOL;
+		ret = -1;
+		goto end_unlock_session;
+	}
+	conn->session->pending_closure_trace_chunk =
+			conn->session->current_trace_chunk;
 	conn->session->current_trace_chunk = published_chunk;
 	published_chunk = NULL;
+end_unlock_session:
 	pthread_mutex_unlock(&conn->session->lock);
-
 end:
 	reply.ret_code = htobe32((uint32_t) reply_code);
 	send_ret = conn->sock->ops->sendmsg(conn->sock,
@@ -2512,13 +2523,23 @@ static int relay_close_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
 		goto end;
 	}
 
+	pthread_mutex_lock(&session->lock);
+	if (session->pending_closure_trace_chunk &&
+			session->pending_closure_trace_chunk != chunk) {
+		ERR("Trace chunk close command for session \"%s\" does not target the trace chunk pending closure",
+				session->session_name);
+		reply_code = LTTNG_ERR_INVALID_PROTOCOL;
+		ret = -1;
+		goto end_unlock_session;
+	}
+
 	chunk_status = lttng_trace_chunk_set_close_timestamp(
 			chunk, close_timestamp);
 	if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 		ERR("Failed to set trace chunk close timestamp");
 		ret = -1;
 		reply_code = LTTNG_ERR_UNK;
-		goto end;
+		goto end_unlock_session;
 	}
 
 	if (close_command.is_set) {
@@ -2527,11 +2548,10 @@ static int relay_close_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
 		if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 			ret = -1;
 			reply_code = LTTNG_ERR_INVALID;
-			goto end;
+			goto end_unlock_session;
 		}
 	}
 
-	pthread_mutex_lock(&session->lock);
 	if (session->current_trace_chunk == chunk) {
 		/*
 		 * After a trace chunk close command, no new streams
@@ -2544,6 +2564,9 @@ static int relay_close_trace_chunk(const struct lttcomm_relayd_hdr *recv_hdr,
 		lttng_trace_chunk_put(session->current_trace_chunk);
 		session->current_trace_chunk = NULL;
 	}
+	lttng_trace_chunk_put(session->pending_closure_trace_chunk);
+	session->pending_closure_trace_chunk = NULL;
+end_unlock_session:
 	pthread_mutex_unlock(&session->lock);
 
 end:
diff --git a/src/bin/lttng-relayd/session.c b/src/bin/lttng-relayd/session.c
index 0997fdd65..28e75f1dc 100644
--- a/src/bin/lttng-relayd/session.c
+++ b/src/bin/lttng-relayd/session.c
@@ -245,6 +245,8 @@ static void destroy_session(struct relay_session *session)
 	assert(!ret);
 	lttng_trace_chunk_put(session->current_trace_chunk);
 	session->current_trace_chunk = NULL;
+	lttng_trace_chunk_put(session->pending_closure_trace_chunk);
+	session->pending_closure_trace_chunk = NULL;
 	ret = sessiond_trace_chunk_registry_session_destroyed(
 			sessiond_trace_chunk_registry, session->sessiond_uuid);
 	assert(!ret);
diff --git a/src/bin/lttng-relayd/session.h b/src/bin/lttng-relayd/session.h
index 8b8ae1f21..6442c17ee 100644
--- a/src/bin/lttng-relayd/session.h
+++ b/src/bin/lttng-relayd/session.h
@@ -120,6 +120,7 @@ struct relay_session {
 	 */
 	struct cds_list_head viewer_session_node;
 	struct lttng_trace_chunk *current_trace_chunk;
+	struct lttng_trace_chunk *pending_closure_trace_chunk;
 	struct rcu_head rcu_node;	/* For call_rcu teardown. */
 };