walwriter_latch.v1.patch

diff --git a/src/backend/postmaster/walwriter.c b/src/backend/postmaster/walwriter.c
index 1411677..2027dd7 100644
--- a/src/backend/postmaster/walwriter.c
+++ b/src/backend/postmaster/walwriter.c
@@ -52,6 +52,7 @@
 #include "storage/bufmgr.h"
 #include "storage/fd.h"
 #include "storage/ipc.h"
+#include "storage/latch.h"
 #include "storage/lwlock.h"
 #include "storage/pmsignal.h"
 #include "storage/smgr.h"
@@ -79,7 +80,11 @@ static void WalShutdownHandler(SIGNAL_ARGS);
 
 
 /*
- * Main entry point for walwriter process
+ * Latch used by signal handlers to wake up the sleep in the main loop.
+ */
+static Latch mainloop_latch;
+
+/* Main entry point for walwriter process
  *
  * This is invoked from BootstrapMain, which has already created the basic
  * execution environment, but not enabled signals yet.
@@ -217,12 +222,16 @@ WalWriterMain(void)
 	PG_SETMASK(&UnBlockSig);
 
 	/*
+	 * Initialize latch used in loop below
+	 */
+	InitLatch(&mainloop_latch);
+
+	/*
 	 * Loop forever
 	 */
 	for (;;)
 	{
-		long		udelay;
-
+		ResetLatch(&mainloop_latch);
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -249,20 +258,8 @@ WalWriterMain(void)
 		 */
 		XLogBackgroundFlush();
 
-		/*
-		 * Delay until time to do something more, but fall out of delay
-		 * reasonably quickly if signaled.
-		 */
-		udelay = WalWriterDelay * 1000L;
-		while (udelay > 999999L)
-		{
-			if (got_SIGHUP || shutdown_requested)
-				break;
-			pg_usleep(1000000L);
-			udelay -= 1000000L;
-		}
-		if (!(got_SIGHUP || shutdown_requested))
-			pg_usleep(udelay);
+		/* We handle all expected signals, so WalWriterDelay timeout won't be invalidated */
+		WaitLatch(&mainloop_latch, WL_LATCH_SET | WL_TIMEOUT | WL_POSTMASTER_DEATH, WalWriterDelay * 1000L);
 	}
 }
 
@@ -309,6 +306,8 @@ static void
 WalSigHupHandler(SIGNAL_ARGS)
 {
 	got_SIGHUP = true;
+	/* let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }
 
 /* SIGTERM: set flag to exit normally */
@@ -316,4 +315,6 @@ static void
 WalShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
+	/* let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }