Small improvements in comments in async.c.

tglsfdc · tglsfdc · commit 6057f61b4d51 · 2015-09-29T22:07:16.000-04:00
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
@@ -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];

Original file line number	Diff line number	Diff line change
`@@ -224,6 +224,7 @@ typedef struct QueueBackendStatus`
`224`	`224`	`* When holding the lock in EXCLUSIVE mode, backends can inspect the entries`
`225`	`225`	`* of other backends and also change the head and tail pointers.`
`226`	`226`	`*`
	`227`	`+ * AsyncCtlLock is used as the control lock for the pg_notify SLRU buffers.`
`227`	`228`	`* In order to avoid deadlocks, whenever we need both locks, we always first`
`228`	`229`	`* get AsyncQueueLock and then AsyncCtlLock.`
`229`	`230`	`*`
`@@ -234,7 +235,7 @@ typedef struct QueueBackendStatus`
`234`	`235`	`typedef struct AsyncQueueControl`
`235`	`236`	`{`
`236`	`237`	`QueuePosition head; /* head points to the next free location */`
`237`		`- QueuePosition tail; /* the global tail is equivalent to the tail`
	`238`	`+ QueuePosition tail; /* the global tail is equivalent to the pos`
`238`	`239`	`* of the "slowest" backend */`
`239`	`240`	`TimestampTz lastQueueFillWarn; /* time of last queue-full msg */`
`240`	`241`	`QueueBackendStatus backend[FLEXIBLE_ARRAY_MEMBER];`