diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index 1fa15a58be3..3277a1cbe68 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -9139,6 +9139,12 @@ CreateCheckPoint(int flags)
 	{
 		do
 		{
+			/*
+			 * Keep absorbing fsync requests while we wait. There could even
+			 * be a deadlock if we don't, if the process that prevents the
+			 * checkpoint is trying to add a request to the queue.
+			 */
+			AbsorbSyncRequests();
 			pg_usleep(10000L);	/* wait for 10 msec */
 		} while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids));
 	}
@@ -9151,6 +9157,7 @@ CreateCheckPoint(int flags)
 	{
 		do
 		{
+			AbsorbSyncRequests();
 			pg_usleep(10000L);	/* wait for 10 msec */
 		} while (HaveVirtualXIDsDelayingChkptEnd(vxids, nvxids));
 	}
diff --git a/src/backend/postmaster/checkpointer.c b/src/backend/postmaster/checkpointer.c
index 624a3238b80..9b2f776579b 100644
--- a/src/backend/postmaster/checkpointer.c
+++ b/src/backend/postmaster/checkpointer.c
@@ -1144,6 +1144,10 @@ CompactCheckpointerRequestQueue(void)
 	/* must hold CheckpointerCommLock in exclusive mode */
 	Assert(LWLockHeldByMe(CheckpointerCommLock));
 
+	/* Avoid memory allocations in a critical section. */
+	if (CritSectionCount > 0)
+		return false;
+
 	/* Initialize skip_slot array */
 	skip_slot = palloc0(sizeof(bool) * CheckpointerShmem->num_requests);