Add assertions checking for the startup process in WAL replay routines

These assertions may prove to become useful to make sure that no process
other than the startup process calls the routines where these checks are
added, as we expect that these do not interfere with a WAL receiver
switched to a "stopping" state by a startup process.

The assumption that only the startup process can use this code has
existed for many years, without a check enforcing it.

Reviewed-by: Xuneng Zhou <xunengzhou@gmail.com>
Discussion: https://postgr.es/m/aQmGeVLYl51y1m_0@paquier.xyz

2 files changed, 6 insertions, 0 deletions

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 8c0d9dbfa8b..9900e3e0179 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9518,6 +9518,8 @@ GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli)
 void
 XLogShutdownWalRcv(void)
 {
+	Assert(AmStartupProcess() || !IsUnderPostmaster);
+
 	ShutdownWalRcv();
 	ResetInstallXLogFileSegmentActive();
 }
diff --git a/src/backend/access/transam/xlogrecovery.c b/src/backend/access/transam/xlogrecovery.c
index 0a5ae5050c4..93c50831b26 100644
--- a/src/backend/access/transam/xlogrecovery.c
+++ b/src/backend/access/transam/xlogrecovery.c
@@ -3148,6 +3148,8 @@ ReadRecord(XLogPrefetcher *xlogprefetcher, int emode,
 	XLogReaderState *xlogreader = XLogPrefetcherGetReader(xlogprefetcher);
 	XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data;
 
+	Assert(AmStartupProcess() || !IsUnderPostmaster);
+
 	/* Pass through parameters to XLogPageRead */
 	private->fetching_ckpt = fetching_ckpt;
 	private->emode = emode;
@@ -3319,6 +3321,8 @@ XLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr, int reqLen,
 	int			r;
 	instr_time	io_start;
 
+	Assert(AmStartupProcess() || !IsUnderPostmaster);
+
 	XLByteToSeg(targetPagePtr, targetSegNo, wal_segment_size);
 	targetPageOff = XLogSegmentOffset(targetPagePtr, wal_segment_size);