Fix: deadlock between UST registry lock and consumer lock

[lttng-tools.git] / src / bin / lttng-sessiond / consumer.c

diff --git a/src/bin/lttng-sessiond/consumer.c b/src/bin/lttng-sessiond/consumer.c
index 166d6c0440202d9798a6bbad8b656fb35bb9432b..2eaca237ff9f60708edbe57b3f40daaac6ba42b2 100644 (file)
--- a/src/bin/lttng-sessiond/consumer.c
+++ b/src/bin/lttng-sessiond/consumer.c
@@ -1157,7 +1157,8 @@ end:
 }
 
 /*
- * Send a close metdata command to consumer using the given channel key.
+ * Send a close metadata command to consumer using the given channel key.
+ * Called with registry lock held.
  *
  * Return 0 on success else a negative value.
  */
@@ -1223,7 +1224,8 @@ end:
 }
 
 /*
- * Send metadata string to consumer. Socket lock MUST be acquired.
+ * Send metadata string to consumer.
+ * RCU read-side lock must be held to guarantee existence of socket.
  *
  * Return 0 on success else a negative value.
  */
@@ -1238,6 +1240,8 @@ int consumer_push_metadata(struct consumer_socket *socket,
 
        DBG2("Consumer push metadata to consumer socket %d", *socket->fd_ptr);
 
+       pthread_mutex_lock(socket->lock);
+
        memset(&msg, 0, sizeof(msg));
        msg.cmd_type = LTTNG_CONSUMER_PUSH_METADATA;
        msg.u.push_metadata.key = metadata_key;
@@ -1265,6 +1269,7 @@ int consumer_push_metadata(struct consumer_socket *socket,
        }
 
 end:
+       pthread_mutex_unlock(socket->lock);
        health_code_update();
        return ret;
 }