Merge branch 'collectd-5.4' into collectd-5.5

[collectd.git] / src / daemon / meta_data.c

diff --git a/src/daemon/meta_data.c b/src/daemon/meta_data.c
index e1d0ec5b71f17a9a284b1a37745416accece939a..29236e2f18563760279d9f3868b2a748e1e1a8a4 100644 (file)
--- a/src/daemon/meta_data.c
+++ b/src/daemon/meta_data.c
@@ -213,6 +213,17 @@ static meta_entry_t *md_entry_lookup (meta_data_t *md, /* {{{ */
   return (e);
 } /* }}} meta_entry_t *md_entry_lookup */
 
+/*
+ * Each value_list_t*, as it is going through the system, is handled by exactly
+ * one thread. Plugins which pass a value_list_t* to another thread, e.g. the
+ * rrdtool plugin, must create a copy first. The meta data within a
+ * value_list_t* is not thread safe and doesn't need to be.
+ *
+ * The meta data associated with cache entries are a different story. There, we
+ * need to ensure exclusive locking to prevent leaks and other funky business.
+ * This is ensured by the uc_meta_data_get_*() functions.
+ */
+
 /*
  * Public functions
  */