diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index d89ba3031f9..395e75f768f 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -1741,7 +1741,7 @@ vacuum_rel(Oid relid, RangeVar *relation, VacuumParams *params)
 		 * MyProc->xid/xmin, otherwise GetOldestNonRemovableTransactionId()
 		 * might appear to go backwards, which is probably Not Good.
 		 */
-		LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+		LWLockAcquire(ProcArrayLock, LW_SHARED);
 		MyProc->statusFlags |= PROC_IN_VACUUM;
 		if (params->is_wraparound)
 			MyProc->statusFlags |= PROC_VACUUM_FOR_WRAPAROUND;
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index f1f4df7d70f..4324e326565 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -181,7 +181,7 @@ StartupDecodingContext(List *output_plugin_options,
 	 */
 	if (!IsTransactionOrTransactionBlock())
 	{
-		LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+		LWLockAcquire(ProcArrayLock, LW_SHARED);
 		MyProc->statusFlags |= PROC_IN_LOGICAL_DECODING;
 		ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
 		LWLockRelease(ProcArrayLock);
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
index 5ed955ba0bf..9c7cf13d4d9 100644
--- a/src/backend/replication/slot.c
+++ b/src/backend/replication/slot.c
@@ -527,7 +527,7 @@ ReplicationSlotRelease(void)
 	MyReplicationSlot = NULL;
 
 	/* might not have been set when we've been a plain slot */
-	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+	LWLockAcquire(ProcArrayLock, LW_SHARED);
 	MyProc->statusFlags &= ~PROC_IN_LOGICAL_DECODING;
 	ProcGlobal->statusFlags[MyProc->pgxactoff] = MyProc->statusFlags;
 	LWLockRelease(ProcArrayLock);
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index e2cb6e990d1..94edb24b22d 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -662,6 +662,8 @@ ProcArrayEndTransaction(PGPROC *proc, TransactionId latestXid)
 		/* avoid unnecessarily dirtying shared cachelines */
 		if (proc->statusFlags & PROC_VACUUM_STATE_MASK)
 		{
+			/* Only safe to change my own flags with just share lock */
+			Assert(proc == MyProc);
 			Assert(!LWLockHeldByMe(ProcArrayLock));
 			LWLockAcquire(ProcArrayLock, LW_SHARED);
 			Assert(proc->statusFlags == ProcGlobal->statusFlags[proc->pgxactoff]);
@@ -682,7 +684,11 @@ ProcArrayEndTransactionInternal(PGPROC *proc, TransactionId latestXid)
 {
 	size_t		pgxactoff = proc->pgxactoff;
 
-	Assert(LWLockHeldByMe(ProcArrayLock));
+	/*
+	 * Note: we need exclusive lock here because we're going to
+	 * change other processes' PGPROC entries.
+	 */
+	Assert(LWLockHeldByMeInMode(ProcArrayLock, LW_EXCLUSIVE));
 	Assert(TransactionIdIsValid(ProcGlobal->xids[pgxactoff]));
 	Assert(ProcGlobal->xids[pgxactoff] == proc->xid);
 
diff --git a/src/backend/storage/lmgr/deadlock.c b/src/backend/storage/lmgr/deadlock.c
index cb7a8f0fd28..f7ed6968ca9 100644
--- a/src/backend/storage/lmgr/deadlock.c
+++ b/src/backend/storage/lmgr/deadlock.c
@@ -623,7 +623,7 @@ FindLockCycleRecurseMember(PGPROC *checkProc,
 					 * because that flag is set at process start and never
 					 * reset.  There is logic elsewhere to avoid canceling an
 					 * autovacuum that is working to prevent XID wraparound
-					 * problems (which needs to read a different vacuumFlag
+					 * problems (which needs to read a different statusFlags
 					 * bit), but we don't do that here to avoid grabbing
 					 * ProcArrayLock.
 					 */
diff --git a/src/include/storage/proc.h b/src/include/storage/proc.h
index 1067f58f51b..00bb244340a 100644
--- a/src/include/storage/proc.h
+++ b/src/include/storage/proc.h
@@ -98,6 +98,11 @@ typedef enum
  * The semaphore and lock-activity fields in a prepared-xact PGPROC are unused,
  * but its myProcLocks[] lists are valid.
  *
+ * We allow many fields of this struct to be accessed without locks, such as
+ * statusFlags or delayChkpt. However, keep in mind that writing mirrored ones
+ * (see below) requires holding ProcArrayLock or XidGenLock in at least shared
+ * mode, so that pgxactoff does not change concurrently.
+ *
  * Mirrored fields:
  *
  * Some fields in PGPROC (see "mirrored in ..." comment) are mirrored into an