Rename two functions that wake up other processes

Instead of talking about setting latches, which is a pretty low-level
mechanism, emphasize that they wake up other processes.

This is in preparation for replacing Latches with a new abstraction.
That's still work in progress, but this seems a little tidier anyway,
so let's get this refactoring out of the way already.

Discussion: https://www.postgresql.org/message-id/391abe21-413e-4d91-a650-b663af49500c%40iki.fi

src/backend/access/transam/xlog.c

@@ -6178,7 +6178,7 @@ StartupXLOG(void)
 	 * Wake up all waiters for replay LSN.  They need to report an error that
 	 * recovery was ended before reaching the target LSN.
 	 */
-	WaitLSNSetLatches(InvalidXLogRecPtr);
+	WaitLSNWakeup(InvalidXLogRecPtr);
 
 	/*
 	 * Shutdown the recovery environment.  This must occur after
@@ -7303,7 +7303,7 @@ CreateCheckPoint(int flags)
 	 * until after the above call that flushes the XLOG_CHECKPOINT_ONLINE
 	 * record.
 	 */
-	SetWalSummarizerLatch();
+	WakeupWalSummarizer();
 
 	/*
 	 * Let smgr do post-checkpoint cleanup (eg, deleting old files).

src/backend/access/transam/xlogrecovery.c

@@ -1837,7 +1837,7 @@ PerformWalRecovery(void)
 			if (waitLSNState &&
 				(XLogRecoveryCtl->lastReplayedEndRecPtr >=
 				 pg_atomic_read_u64(&waitLSNState->minWaitedLSN)))
-				WaitLSNSetLatches(XLogRecoveryCtl->lastReplayedEndRecPtr);
+				WaitLSNWakeup(XLogRecoveryCtl->lastReplayedEndRecPtr);
 
 			/* Else, try to fetch the next WAL record */
 			record = ReadRecord(xlogprefetcher, LOG, false, replayTLI);

src/backend/access/transam/xlogwait.c

@@ -151,7 +151,7 @@ deleteLSNWaiter(void)
  * and set latches for all waiters.
  */
 void
-WaitLSNSetLatches(XLogRecPtr currentLSN)
+WaitLSNWakeup(XLogRecPtr currentLSN)
 {
 	int			i;
 	ProcNumber *wakeUpProcs;

src/backend/postmaster/walsummarizer.c

@@ -626,7 +626,7 @@ GetOldestUnsummarizedLSN(TimeLineID *tli, bool *lsn_is_exact)
 }
 
 /*
- * Attempt to set the WAL summarizer's latch.
+ * Wake up the WAL summarizer process.
  *
  * This might not work, because there's no guarantee that the WAL summarizer
  * process was successfully started, and it also might have started but
@@ -634,7 +634,7 @@ GetOldestUnsummarizedLSN(TimeLineID *tli, bool *lsn_is_exact)
  * latch set, but there's no guarantee.
  */
 void
-SetWalSummarizerLatch(void)
+WakeupWalSummarizer(void)
 {
 	ProcNumber	pgprocno;
 

src/include/access/xlogwait.h

@@ -82,7 +82,7 @@ extern PGDLLIMPORT WaitLSNState *waitLSNState;
 
 extern Size WaitLSNShmemSize(void);
 extern void WaitLSNShmemInit(void);
-extern void WaitLSNSetLatches(XLogRecPtr currentLSN);
+extern void WaitLSNWakeup(XLogRecPtr currentLSN);
 extern void WaitLSNCleanup(void);
 extern WaitLSNResult WaitForLSNReplay(XLogRecPtr targetLSN, int64 timeout);
 

src/include/postmaster/walsummarizer.h

@@ -29,7 +29,7 @@ extern void GetWalSummarizerState(TimeLineID *summarized_tli,
 								  int *summarizer_pid);
 extern XLogRecPtr GetOldestUnsummarizedLSN(TimeLineID *tli,
 										   bool *lsn_is_exact);
-extern void SetWalSummarizerLatch(void);
+extern void WakeupWalSummarizer(void);
 extern void WaitForWalSummarization(XLogRecPtr lsn);
 
 #endif