Remove redundant HandleWalWriterInterrupts().

Because of commit 1bdd54e, the code of HandleWalWriterInterrupts()
became the same as HandleMainLoopInterrupts(). So this commit removes
HandleWalWriterInterrupts() and makes walwriter use
HandleMainLoopInterrupts() for improved code simplicity.

Author: Fujii Masao
Reviewed-by: Bharath Rupireddy, Nathan Bossart
Discussion: https://postgr.es/m/CAHGQGwHUtwCsB4DnqFLiMiVzjcA=zmeCKf9_pgQM-yJopydatw@mail.gmail.com

Author: MasaoFujii

src/backend/postmaster/walwriter.c

@@ -78,9 +78,6 @@ int			WalWriterFlushAfter = DEFAULT_WAL_WRITER_FLUSH_AFTER;
 #define LOOPS_UNTIL_HIBERNATE		50
 #define HIBERNATE_FACTOR			25
 
-/* Prototypes for private functions */
-static void HandleWalWriterInterrupts(void);
-
 /*
  * Main entry point for walwriter process
  *
@@ -245,7 +242,7 @@ WalWriterMain(void)
 		ResetLatch(MyLatch);
 
 		/* Process any signals received recently */
-		HandleWalWriterInterrupts();
+		HandleMainLoopInterrupts();
 
 		/*
 		 * Do what we're here for; then, if XLogBackgroundFlush() found useful
@@ -275,26 +272,3 @@ WalWriterMain(void)
 						 WAIT_EVENT_WAL_WRITER_MAIN);
 	}
 }
-
-/*
- * Interrupt handler for main loops of WAL writer process.
- */
-static void
-HandleWalWriterInterrupts(void)
-{
-	if (ProcSignalBarrierPending)
-		ProcessProcSignalBarrier();
-
-	if (ConfigReloadPending)
-	{
-		ConfigReloadPending = false;
-		ProcessConfigFile(PGC_SIGHUP);
-	}
-
-	if (ShutdownRequestPending)
-		proc_exit(0);
-
-	/* Perform logging of memory contexts of this process */
-	if (LogMemoryContextPending)
-		ProcessLogMemoryContextInterrupt();
-}