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 9b8a0a759ac5f22acb16979ed468bf6d1c87f16f..b7394d97d2def451211fcf1d993d77350340ca8c 100644 (file)
--- a/src/bin/lttng-sessiond/consumer.c
+++ b/src/bin/lttng-sessiond/consumer.c
@@ -1158,7 +1158,8 @@ 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.
  */
  *
  * Return 0 on success else a negative value.
  */


@@ -1224,7 +1225,8 @@ 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.
  */
  *
  * Return 0 on success else a negative value.
  */


@@ -1239,6 +1241,8 @@ int consumer_push_metadata(struct consumer_socket *socket,
 
        DBG2("Consumer push metadata to consumer socket %d", *socket->fd_ptr);
 
 
        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;
        memset(&msg, 0, sizeof(msg));
        msg.cmd_type = LTTNG_CONSUMER_PUSH_METADATA;
        msg.u.push_metadata.key = metadata_key;


@@ -1266,6 +1270,7 @@ int consumer_push_metadata(struct consumer_socket *socket,
        }
 
 end:
        }
 
 end:

+       pthread_mutex_unlock(socket->lock);

        health_code_update();
        return ret;
 }
        health_code_update();
        return ret;
 }