archiver_power.patch

diff --git a/src/backend/postmaster/pgarch.c b/src/backend/postmaster/pgarch.c
index b40375a..01e5350 100644
--- a/src/backend/postmaster/pgarch.c
+++ b/src/backend/postmaster/pgarch.c
@@ -44,6 +44,7 @@
 #include "storage/pmsignal.h"
 #include "utils/guc.h"
 #include "utils/ps_status.h"
+#include "storage/latch.h"
 
 
 /* ----------
@@ -87,6 +88,12 @@ static volatile sig_atomic_t got_SIGTERM = false;
 static volatile sig_atomic_t wakened = false;
 static volatile sig_atomic_t ready_to_stop = false;
 
+/*
+ * Latch that archiver loop waits on until it is awakened by 
+ * signals, each of which there is a handler for
+ */
+static volatile Latch mainloop_latch;
+
 /* ----------
  * Local function forward declarations
  * ----------
@@ -228,6 +235,8 @@ PgArchiverMain(int argc, char *argv[])
 
 	MyProcPid = getpid();		/* reset MyProcPid */
 
+	InitLatch(&mainloop_latch); /* initialise latch used in main loop, now that we are a subprocess */
+
 	MyStartTime = time(NULL);	/* record Start Time for logging */
 
 	/*
@@ -282,6 +291,8 @@ ArchSigHupHandler(SIGNAL_ARGS)
 {
 	/* set flag to re-read config file at next convenient time */
 	got_SIGHUP = true;
+	/* Let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }
 
 /* SIGTERM signal handler for archiver process */
@@ -295,6 +306,8 @@ ArchSigTermHandler(SIGNAL_ARGS)
 	 * archive commands.
 	 */
 	got_SIGTERM = true;
+	/* Let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }
 
 /* SIGUSR1 signal handler for archiver process */
@@ -303,6 +316,8 @@ pgarch_waken(SIGNAL_ARGS)
 {
 	/* set flag that there is work to be done */
 	wakened = true;
+	/* Let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }
 
 /* SIGUSR2 signal handler for archiver process */
@@ -311,6 +326,8 @@ pgarch_waken_stop(SIGNAL_ARGS)
 {
 	/* set flag to do a final cycle and shut down afterwards */
 	ready_to_stop = true;
+	/* Let the waiting loop iterate */
+	SetLatch(&mainloop_latch);
 }
 
 /*
@@ -334,6 +351,13 @@ pgarch_MainLoop(void)
 
 	do
 	{
+		/*
+		 * There shouldn't be anything for the archiver to do except to wait
+		 * on a latch ... however, the archiver exists to protect our data,
+		 * so she wakes up occasionally to allow herself to be proactive.
+		 */
+		ResetLatch(&mainloop_latch);
+
 		/* When we get SIGUSR2, we do one more archive cycle, then exit */
 		time_to_stop = ready_to_stop;
 
@@ -370,28 +394,28 @@ pgarch_MainLoop(void)
 			last_copy_time = time(NULL);
 		}
 
-		/*
-		 * There shouldn't be anything for the archiver to do except to wait
-		 * for a signal ... however, the archiver exists to protect our data,
-		 * so she wakes up occasionally to allow herself to be proactive.
+		/* 
+		 * Wait on latch, until various signals are received, or 
+		 * until a poll will be forced by PGARCH_AUTOWAKE_INTERVAL
+		 * having passed since last_copy_time
 		 *
-		 * On some platforms, signals won't interrupt the sleep.  To ensure we
-		 * respond reasonably promptly when someone signals us, break down the
-		 * sleep into 1-second increments, and check for interrupts after each
-		 * nap.
+		 * The caveat about signals invalidating the timeout of 
+		 * WaitLatch() on some platforms can be safely disregarded, 
+		 * because we handle all expected signals, and all handlers 
+		 * call SetLatch() where that matters anyway
 		 */
-		while (!(wakened || ready_to_stop || got_SIGHUP ||
-				 !PostmasterIsAlive(true)))
-		{
-			time_t		curtime;
 
-			pg_usleep(1000000L);
+		if (!time_to_stop) /* Don't wait during last iteration */
+		{
+			time_t		 curtime = time(NULL);	
+			unsigned int timeout_secs  = (unsigned int) PGARCH_AUTOWAKE_INTERVAL - 
+					(unsigned int) (curtime - last_copy_time);
+			WaitLatch(&mainloop_latch, timeout_secs * 1000000L);
 			curtime = time(NULL);
 			if ((unsigned int) (curtime - last_copy_time) >=
 				(unsigned int) PGARCH_AUTOWAKE_INTERVAL)
-				wakened = true;
+				wakened = true; /* wakened by timeout - this wasn't a SIGHUP, etc */
 		}
-
 		/*
 		 * The archiver quits either when the postmaster dies (not expected)
 		 * or after completing one more archiving cycle after receiving