From 6057f61b4d511d8321f295d827ced13809e5a1ae Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 29 Sep 2015 22:06:59 -0400
Subject: [PATCH] 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".
---
src/backend/commands/async.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 3b71174b826..91baede4e36 100644
--- 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];
--
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