Small improvements in comments in async.c.

We seem to have lost a line somewhere along the way in the comment block
that discusses async.c's locks, because it suddenly refers to "both locks"
without previously having mentioned more than one.  Add a sentence to make
that read more sanely.  Also, refer to the "pos of the slowest backend"
not the "tail of the slowest backend", since we have no per-backend value
called "tail".

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 3b71174b82640a9118ced2d771a083e59f9603f6..91baede4e363f148e00bae53f9d6bdd4a1d5f4a3 100644 (file)
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -224,6 +224,7 @@ typedef struct QueueBackendStatus
  * When holding the lock in EXCLUSIVE mode, backends can inspect the entries
  * of other backends and also change the head and tail pointers.
  *
+ * AsyncCtlLock is used as the control lock for the pg_notify SLRU buffers.
  * In order to avoid deadlocks, whenever we need both locks, we always first
  * get AsyncQueueLock and then AsyncCtlLock.
  *
@@ -234,7 +235,7 @@ typedef struct QueueBackendStatus
 typedef struct AsyncQueueControl
 {
        QueuePosition head;                     /* head points to the next free location */
-       QueuePosition tail;                     /* the global tail is equivalent to the tail
+       QueuePosition tail;                     /* the global tail is equivalent to the pos
                                                                 * of the "slowest" backend */
        TimestampTz lastQueueFillWarn;          /* time of last queue-full msg */
        QueueBackendStatus backend[FLEXIBLE_ARRAY_MEMBER];