From 64638ccba3a659d8b8a3a4bc5b47307685a64a8a Mon Sep 17 00:00:00 2001
From: Fujii Masao <fujii@postgresql.org>
Date: Mon, 30 Mar 2020 17:35:03 +0900
Subject: [PATCH] Report waiting via PS while recovery is waiting for buffer
 pin in hot standby.

Previously while the startup process was waiting for the recovery conflict
with snapshot, tablespace or lock to be resolved, waiting was reported in
PS display, but not in the case of recovery conflict with buffer pin.
This commit makes the startup process in hot standby report waiting via PS
while waiting for the conflicts with other backends holding buffer pins to
be resolved.

Author: Masahiko Sawada
Reviewed-by: Fujii Masao
Discussion: https://postgr.es/m/CA+fd4k4mXWTwfQLS3RPwGr4xnfAEs1ysFfgYHvmmoUgv6Zxvmg@mail.gmail.com
---
 src/backend/storage/buffer/bufmgr.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index e05e2b3456..e72d607a23 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -49,6 +49,7 @@
 #include "storage/proc.h"
 #include "storage/smgr.h"
 #include "storage/standby.h"
+#include "utils/ps_status.h"
 #include "utils/rel.h"
 #include "utils/resowner_private.h"
 #include "utils/timestamp.h"
@@ -3616,6 +3617,7 @@ void
 LockBufferForCleanup(Buffer buffer)
 {
 	BufferDesc *bufHdr;
+	char	   *new_status = NULL;
 
 	Assert(BufferIsValid(buffer));
 	Assert(PinCountWaitBuf == NULL);
@@ -3650,6 +3652,13 @@ LockBufferForCleanup(Buffer buffer)
 		{
 			/* Successfully acquired exclusive lock with pincount 1 */
 			UnlockBufHdr(bufHdr, buf_state);
+
+			/* Report change to non-waiting status */
+			if (new_status)
+			{
+				set_ps_display(new_status);
+				pfree(new_status);
+			}
 			return;
 		}
 		/* Failed, so mark myself as waiting for pincount 1 */
@@ -3668,6 +3677,20 @@ LockBufferForCleanup(Buffer buffer)
 		/* Wait to be signaled by UnpinBuffer() */
 		if (InHotStandby)
 		{
+			/* Report change to waiting status */
+			if (update_process_title && new_status == NULL)
+			{
+				const char *old_status;
+				int			len;
+
+				old_status = get_ps_display(&len);
+				new_status = (char *) palloc(len + 8 + 1);
+				memcpy(new_status, old_status, len);
+				strcpy(new_status + len, " waiting");
+				set_ps_display(new_status);
+				new_status[len] = '\0'; /* truncate off " waiting" */
+			}
+
 			/* Publish the bufid that Startup process waits on */
 			SetStartupBufferPinWaitBufId(buffer - 1);
 			/* Set alarm and then wait to be signaled by UnpinBuffer() */