[evolution-data-server/gnome-3-26] Extend a developer comment of camel_message_info_property_lock()

[Milan Crha <mcrha src gnome org>]

commit f1cbd5ef6dced0ffb5dfe5eaea92585cb9a9095a
Author: Milan Crha <mcrha redhat com>
Date:   Tue Oct 10 19:23:07 2017 +0200

    Extend a developer comment of camel_message_info_property_lock()
    
    Related to bug 788782.

 src/camel/camel-message-info.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/camel/camel-message-info.c b/src/camel/camel-message-info.c
index b2c5f08..fc4bc8f 100644
--- a/src/camel/camel-message-info.c
+++ b/src/camel/camel-message-info.c
@@ -1151,6 +1151,12 @@ camel_message_info_ref_summary (const CamelMessageInfo *mi)
  * when properties are changing. Release the lock with
  * camel_message_info_property_unlock().
  *
+ * Note: Make sure the CamelFolderSummary lock is held before this lock,
+ * if there will be called any 'set' function on the @mi, to avoid deadlock
+ * when the summary would be set as dirty while another thread might try
+ * to read values from the @mi, waiting for the property lock and holding
+ * the summary lock at the same time.
+ *
  * Since: 3.24
  **/
 void