latches-1.patch

diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c
index 615a7fa..094d0c9 100644
--- a/src/backend/access/transam/twophase.c
+++ b/src/backend/access/transam/twophase.c
@@ -55,6 +55,7 @@
 #include "miscadmin.h"
 #include "pg_trace.h"
 #include "pgstat.h"
+#include "replication/walsender.h"
 #include "storage/fd.h"
 #include "storage/procarray.h"
 #include "storage/sinvaladt.h"
@@ -1025,6 +1026,13 @@ EndPrepare(GlobalTransaction gxact)
 
 	/* If we crash now, we have prepared: WAL replay will fix things */
 
+	/*
+	 * Wake up all walsenders to send WAL up to the PREPARE record
+	 * immediately if replication is enabled
+	 */
+	if (max_wal_senders > 0)
+		WalSndWakeup();
+
 	/* write correct CRC and close file */
 	if ((write(fd, &statefile_crc, sizeof(pg_crc32))) != sizeof(pg_crc32))
 	{
@@ -2005,6 +2013,13 @@ RecordTransactionCommitPrepared(TransactionId xid,
 	/* Flush XLOG to disk */
 	XLogFlush(recptr);
 
+	/*
+	 * Wake up all walsenders to send WAL up to the COMMIT PREPARED record
+	 * immediately if replication is enabled
+	 */
+	if (max_wal_senders > 0)
+		WalSndWakeup();
+
 	/* Mark the transaction committed in pg_clog */
 	TransactionIdCommitTree(xid, nchildren, children);
 
@@ -2078,6 +2093,13 @@ RecordTransactionAbortPrepared(TransactionId xid,
 	XLogFlush(recptr);
 
 	/*
+	 * Wake up all walsenders to send WAL up to the ABORT PREPARED record
+	 * immediately if replication is enabled
+	 */
+	if (max_wal_senders > 0)
+		WalSndWakeup();
+
+	/*
 	 * Mark the transaction aborted in clog.  This is not absolutely necessary
 	 * but we may as well do it while we are here.
 	 */
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6bcc55c..942d5c2 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -36,6 +36,7 @@
 #include "libpq/be-fsstubs.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "replication/walsender.h"
 #include "storage/bufmgr.h"
 #include "storage/fd.h"
 #include "storage/lmgr.h"
@@ -1068,6 +1069,13 @@ RecordTransactionCommit(void)
 		XLogFlush(XactLastRecEnd);
 
 		/*
+		 * Wake up all walsenders to send WAL up to the COMMIT record
+		 * immediately if replication is enabled
+		 */
+		if (max_wal_senders > 0)
+			WalSndWakeup();
+
+		/*
 		 * Now we may update the CLOG, if we wrote a COMMIT record above
 		 */
 		if (markXidCommitted)
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index 53c2581..9f5d1af 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -66,9 +66,6 @@ bool		am_walsender = false;		/* Am I a walsender process ? */
 int			max_wal_senders = 0;	/* the maximum number of concurrent walsenders */
 int			WalSndDelay = 200;	/* max sleep time between some actions */
 
-#define NAPTIME_PER_CYCLE 100000L		/* max sleep time between cycles
-										 * (100ms) */
-
 /*
  * These variables are used similarly to openLogFile/Id/Seg/Off,
  * but for walsender to read the XLOG.
@@ -93,6 +90,7 @@ static volatile sig_atomic_t ready_to_stop = false;
 static void WalSndSigHupHandler(SIGNAL_ARGS);
 static void WalSndShutdownHandler(SIGNAL_ARGS);
 static void WalSndQuickDieHandler(SIGNAL_ARGS);
+static void WalSndXLogSendHandler(SIGNAL_ARGS);
 static void WalSndLastCycleHandler(SIGNAL_ARGS);
 
 /* Prototypes for private functions */
@@ -144,6 +142,16 @@ WalSenderMain(void)
 	/* Handle handshake messages before streaming */
 	WalSndHandshake();
 
+	/* Initialize shared memory status */
+	{
+		/* use volatile pointer to prevent code rearrangement */
+		volatile WalSnd *walsnd = MyWalSnd;
+
+		SpinLockAcquire(&walsnd->mutex);
+		walsnd->sentPtr = sentPtr;
+		SpinLockRelease(&walsnd->mutex);
+	}
+
 	/* Main loop of walsender */
 	return WalSndLoop();
 }
@@ -380,8 +388,6 @@ WalSndLoop(void)
 	/* Loop forever, unless we get an error */
 	for (;;)
 	{
-		long		remain;		/* remaining time (us) */
-
 		/*
 		 * Emergency bailout if postmaster has died.  This is to avoid the
 		 * necessity for manual cleanup of all postmaster children.
@@ -421,32 +427,41 @@ WalSndLoop(void)
 		/*
 		 * If we had sent all accumulated WAL in last round, nap for the
 		 * configured time before retrying.
-		 *
-		 * On some platforms, signals won't interrupt the sleep.  To ensure we
-		 * respond reasonably promptly when someone signals us, break down the
-		 * sleep into NAPTIME_PER_CYCLE increments, and check for interrupts
-		 * after each nap.
 		 */
 		if (caughtup)
 		{
-			remain = WalSndDelay * 1000L;
-			while (remain > 0)
-			{
-				/* Check for interrupts */
-				if (got_SIGHUP || shutdown_requested || ready_to_stop)
-					break;
+			/*
+			 * Even if we wrote all the WAL that was available when we started
+			 * sending, more might have arrived while we were sending this
+			 * batch. We had the latch set while sending, so we have not
+			 * received any signals from that time. Let's arm the latch
+			 * again, and after that check that we're still up-to-date.
+			 */
+			ResetLatch(&MyWalSnd->latch);
 
-				/* Sleep and check that the connection is still alive */
-				pg_usleep(remain > NAPTIME_PER_CYCLE ? NAPTIME_PER_CYCLE : remain);
-				CheckClosedConnection();
+			if (!XLogSend(output_message, &caughtup))
+				break;
+			if (caughtup && !got_SIGHUP && !ready_to_stop && !shutdown_requested)
+			{
+				/*
+				 * XXX: Should we invent an API to wait for data coming from the
+				 * client connection too? It's not critical, but we could then
+				 * eliminate the timeout altogether and go to sleep for good.
+				 */
 
-				remain -= NAPTIME_PER_CYCLE;
+				/* Sleep */
+				WaitLatch(&MyWalSnd->latch, WalSndDelay * 1000);
 			}
-		}
 
-		/* Attempt to send the log once every loop */
-		if (!XLogSend(output_message, &caughtup))
-			break;
+			/* Check if the connection was closed */
+			CheckClosedConnection();
+		}
+		else
+		{
+			/* Attempt to send the log once every loop */
+			if (!XLogSend(output_message, &caughtup))
+				break;
+		}
 	}
 
 	/*
@@ -493,10 +508,15 @@ InitWalSnd(void)
 		}
 		else
 		{
-			/* found */
-			MyWalSnd = (WalSnd *) walsnd;
+			/*
+			 * Found a free slot. Take ownership of the latch and initialize
+			 * the other fields.
+			 */
+			InitLatch((Latch *) &walsnd->latch);
 			walsnd->pid = MyProcPid;
-			MemSet(&MyWalSnd->sentPtr, 0, sizeof(XLogRecPtr));
+			MemSet(&walsnd->sentPtr, 0, sizeof(XLogRecPtr));
+			/* Set MyWalSnd only after it's fully initialized. */
+			MyWalSnd = (WalSnd *) walsnd;
 			SpinLockRelease(&walsnd->mutex);
 			break;
 		}
@@ -523,6 +543,7 @@ WalSndKill(int code, Datum arg)
 	 * for this.
 	 */
 	MyWalSnd->pid = 0;
+	ReleaseLatch(&MyWalSnd->latch);
 
 	/* WalSnd struct isn't mine anymore */
 	MyWalSnd = NULL;
@@ -787,6 +808,8 @@ static void
 WalSndSigHupHandler(SIGNAL_ARGS)
 {
 	got_SIGHUP = true;
+	if (MyWalSnd)
+		SetLatch(&MyWalSnd->latch);
 }
 
 /* SIGTERM: set flag to shut down */
@@ -794,6 +817,8 @@ static void
 WalSndShutdownHandler(SIGNAL_ARGS)
 {
 	shutdown_requested = true;
+	if (MyWalSnd)
+		SetLatch(&MyWalSnd->latch);
 }
 
 /*
@@ -828,11 +853,20 @@ WalSndQuickDieHandler(SIGNAL_ARGS)
 	exit(2);
 }
 
+/* SIGUSR1: set flag to send WAL records */
+static void
+WalSndXLogSendHandler(SIGNAL_ARGS)
+{
+	latch_sigusr1_handler();
+}
+
 /* SIGUSR2: set flag to do a last cycle and shut down afterwards */
 static void
 WalSndLastCycleHandler(SIGNAL_ARGS)
 {
 	ready_to_stop = true;
+	if (MyWalSnd)
+		SetLatch(&MyWalSnd->latch);
 }
 
 /* Set up signal handlers */
@@ -847,7 +881,7 @@ WalSndSignals(void)
 	pqsignal(SIGQUIT, WalSndQuickDieHandler);	/* hard crash time */
 	pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
-	pqsignal(SIGUSR1, SIG_IGN); /* not used */
+	pqsignal(SIGUSR1, WalSndXLogSendHandler);	/* request WAL sending */
 	pqsignal(SIGUSR2, WalSndLastCycleHandler);	/* request a last cycle and
 												 * shutdown */
 
@@ -895,6 +929,16 @@ WalSndShmemInit(void)
 	}
 }
 
+/* Wake up all walsenders */
+void
+WalSndWakeup(void)
+{
+	int		i;
+
+	for (i = 0; i < max_wal_senders; i++)
+		SetLatch(&WalSndCtl->walsnds[i].latch);
+}
+
 /*
  * This isn't currently used for anything. Monitoring tools might be
  * interested in the future, and we'll need something like this in the
diff --git a/src/backend/storage/ipc/Makefile b/src/backend/storage/ipc/Makefile
index a5da0ec..5cbc515 100644
--- a/src/backend/storage/ipc/Makefile
+++ b/src/backend/storage/ipc/Makefile
@@ -15,7 +15,7 @@ override CFLAGS+= -fno-inline
 endif
 endif
 
-OBJS = ipc.o ipci.o pmsignal.o procarray.o procsignal.o shmem.o shmqueue.o \
-	sinval.o sinvaladt.o standby.o
+OBJS = ipc.o ipci.o latch.o pmsignal.o procarray.o procsignal.o shmem.o \
+       shmqueue.o sinval.o sinvaladt.o standby.o
 
 include $(top_srcdir)/src/backend/common.mk
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index 492ac9a..0083513 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -30,6 +30,7 @@
 #include "replication/walsender.h"
 #include "storage/bufmgr.h"
 #include "storage/ipc.h"
+#include "storage/latch.h"
 #include "storage/pg_shmem.h"
 #include "storage/pmsignal.h"
 #include "storage/procarray.h"
@@ -117,6 +118,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 		size = add_size(size, SInvalShmemSize());
 		size = add_size(size, PMSignalShmemSize());
 		size = add_size(size, ProcSignalShmemSize());
+		size = add_size(size, LatchShmemSize());
 		size = add_size(size, BgWriterShmemSize());
 		size = add_size(size, AutoVacuumShmemSize());
 		size = add_size(size, WalSndShmemSize());
@@ -217,6 +219,7 @@ CreateSharedMemoryAndSemaphores(bool makePrivate, int port)
 	 */
 	PMSignalShmemInit();
 	ProcSignalShmemInit();
+	LatchShmemInit();
 	BgWriterShmemInit();
 	AutoVacuumShmemInit();
 	WalSndShmemInit();
diff --git a/src/backend/storage/ipc/latch.c b/src/backend/storage/ipc/latch.c
new file mode 100644
index 0000000..1becf7a
--- /dev/null
+++ b/src/backend/storage/ipc/latch.c
@@ -0,0 +1,306 @@
+/*-------------------------------------------------------------------------
+ *
+ * latch.c
+ *	  Routines for interprocess latches
+ *
+ * A latch allows you to wait until another process, or a signal handler
+ * within the same process, wakes you up. There is three basic operations
+ * on a latch:
+ *
+ * SetLatch		- Sets the latch
+ * ResetLatch	- Clears the latch, allowing it to be set again
+ * WaitLatch	- waits for the latch to become set
+ *
+ * These can be used to wait for an event, without the race conditions
+ * involved with e.g plain Unix signals and select(). pselect() was
+ * invented to solve the same problem, but it is not portable enough.
+ *
+ * The implementation is such that setting a latch that's already set
+ * is quick.
+ *
+ * The pattern to wait on an event is:
+ *
+ * for (;;)
+ * {
+ *     WaitLatch();
+ *     ResetLatch();
+ *
+ *     if (work to do)
+ *         Do Stuff();
+ * }
+ *
+ * It's important to reset the latch *before* checking if there's work to
+ * do. Otherwise, if someone sets the latch between the check and the
+ * ResetLatch call, you will miss it and Wait will block.
+ *
+ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include <fcntl.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "miscadmin.h"
+#include "replication/walsender.h"
+#include "storage/latch.h"
+#include "storage/shmem.h"
+
+/* Read and write end of the self-pipe */
+static int selfpipe_readfd;
+static int selfpipe_writefd;
+
+/* Are we currently in WaitLatch()? The signal handler would like to know. */
+static volatile sig_atomic_t waiting = false;
+
+/* private function prototypes */
+static void drainSelfPipe(void);
+static void sendSelfPipeByte(void);
+
+/*
+ * Initialize a backend-local latch.
+ */
+void
+InitLatch(Latch *latch)
+{
+	Assert(latch->owner_pid == 0);
+	latch->owner_pid = MyProcPid;
+	latch->is_set = false;
+}
+
+/*
+ * Initialize an inter-process latch. Like InitLatch(), but the latch can
+ * be triggered from another process. A process that needs to wait on
+ * an inter-proess latch also needs to ensure that latch_sigusr1_handler()
+ * is called from the SIGUSR1 signal handler.
+ */
+void
+InitSharedLatch(Latch *latch)
+{
+	/*
+	 * This is the same as InitLatch() in this implementation. The
+	 * Windows implementation will likely differ.
+	 */
+	InitLatch(latch);
+}
+
+/*
+ * Release a latch previously allocated with InitLatch() or InitShareLatch().
+ */
+void
+ReleaseLatch(Latch *latch)
+{
+	Assert(latch->owner_pid == MyProcPid);
+	latch->owner_pid = 0;
+}
+
+/*
+ * Wait for given latch to be set, or until 'timeout' milliseconds passes.
+ * If 'timeout' is 0, wait forever. If the latch is already set, returns
+ * immediately.
+ *
+ * The latch must have been previously initialized by the current process.
+ */
+void
+WaitLatch(Latch *latch, long timeout)
+{
+	struct timeval tv;
+	fd_set		input_mask;
+	int			rc;
+
+	if (latch->owner_pid != MyProcPid)
+		elog(ERROR, "cannot wait on a latch now owned by current process");
+
+	waiting = true;
+	for (;;)
+	{
+		/*
+		 * Clear the pipe, and check if the latch is set already. If someone
+		 * sets the latch between this and the select() below, the setter
+		 * will write a byte to the pipe (or signal us and the signal handler
+		 * will do that), and the select() will return immediately.
+		 */
+		drainSelfPipe();
+		if (latch->is_set)
+			break;
+
+		/* Sleep */
+		if (timeout > 0)
+		{
+			tv.tv_sec = timeout / 1000000L;
+			tv.tv_usec = timeout % 1000000L;
+		}
+
+		FD_ZERO(&input_mask);
+		FD_SET(selfpipe_readfd, &input_mask);
+
+		rc = select(selfpipe_readfd + 1, &input_mask, NULL, NULL,
+					(timeout > 0) ? &tv : NULL);
+		if (rc < 0)
+		{
+			if (errno != EINTR)
+				ereport(ERROR,
+						(errcode_for_socket_access(),
+						 errmsg("select() failed: %m")));
+		}
+		if (rc == 0)
+			break;		/* timeout exceeded */
+	}
+	waiting = false;
+}
+
+/*
+ * Sets a latch and wakes up anyone waiting on it. Returns quickly if the
+ * latch is set already.
+ */
+void
+SetLatch(Latch *latch)
+{
+	pid_t owner_pid;
+
+	/* Quick exit if already set */
+	if (latch->is_set)
+		return;
+
+	latch->is_set = true;
+
+	/*
+	 * See if anyone's waiting for the latch. It can be the current process
+	 * if we're in a signal handler. We use the self-pipe to wake up the
+	 * select() in that case. If it's another process, send a signal.
+	 */
+	owner_pid = latch->owner_pid;
+	if (owner_pid == 0)
+		return;
+	else if (owner_pid == MyProcPid)
+		sendSelfPipeByte();
+	else
+		kill(owner_pid, SIGUSR1);
+}
+
+/*
+ * Clear the latch. Calling WaitLatch after this will sleep, unless
+ * the latch is set again before the WaitLatch call.
+ */
+void
+ResetLatch(Latch *latch)
+{
+	/* Only the owner should reset the latch */
+	Assert(latch->owner_pid == MyProcPid);
+
+	if (!latch->is_set)
+		return;
+
+	latch->is_set = false;
+}
+
+/*
+ * Unused in this implementation, but Windows will need this.
+ */
+static int
+NumSharedLatches(void)
+{
+	int numLatches = 0;
+
+	/* Each walsender needs one latch */
+	numLatches += max_wal_senders;
+
+	return numLatches;
+}
+
+/*
+ * LatchShmemSize
+ *		Compute space needed for latch's shared memory
+ */
+Size
+LatchShmemSize(void)
+{
+	return 0;
+}
+
+/*
+ * LatchShmemInit
+ *		Allocate and initialize shared memory needed for latches
+ */
+void
+LatchShmemInit(void)
+{
+	int pipefd[2];
+
+	/*
+	 * Set up a pipe that allows a signal handler to wake up the select()
+	 * in WaitLatch(). Make the write-end non-blocking, so that SetLatch()
+	 * won't block if the event has already been set many times filling
+	 * the kernel buffer. Make the read-end non-blocking too, so that we
+	 * can easily clear the pipe by reading until EAGAIN or EWOULDBLOCK.
+	 */
+	if (pipe(pipefd) < 0)
+		elog(FATAL, "pipe() failed: %m");
+	if (fcntl(pipefd[0], F_SETFL, O_NONBLOCK) < 0)
+		elog(FATAL, "fcntl() failed on read-end of self-pipe: %m");
+	if (fcntl(pipefd[1], F_SETFL, O_NONBLOCK) < 0)
+		elog(FATAL, "fcntl() failed on write-end of self-pipe: %m");
+
+	selfpipe_readfd = pipefd[0];
+	selfpipe_writefd = pipefd[1];
+}
+
+void
+latch_sigusr1_handler(void)
+{
+	if (waiting)
+		sendSelfPipeByte();
+}
+
+/* Send one byte to the self-pipe, to wake up WaitLatch() */
+static void
+sendSelfPipeByte(void)
+{
+	int rc;
+	char dummy = 0;
+
+retry:
+	rc = write(selfpipe_writefd, &dummy, 1);
+	if (rc < 0)
+	{
+		if (errno != EAGAIN && errno != EWOULDBLOCK)
+		{
+			/*
+			 * XXX: Is it safe to elog(ERROR) in a signal handler?
+			 */
+			elog(ERROR, "write() on self-pipe failed: %m");
+		}
+		if (errno == EINTR)
+			goto retry;
+	}
+}
+
+/* Read all available data from the self-pipe */
+static void
+drainSelfPipe(void)
+{
+	int rc;
+	char buf;
+
+	for (;;)
+	{
+		rc = read(selfpipe_readfd, &buf, 1);
+		if (rc < 0)
+		{
+			if (errno == EINTR)
+				continue;
+			if (errno == EAGAIN || errno == EWOULDBLOCK)
+				break;		/* the pipe is empty */
+
+			elog(ERROR, "read() on self-pipe failed: %m");
+		}
+		else if (rc == 0)
+			elog(ERROR, "unexpected EOF on self-pipe");
+	}
+}
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 2340236..2ad2ad9 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -278,5 +278,7 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_BUFFERPIN);
 
+	latch_sigusr1_handler();
+
 	errno = save_errno;
 }
diff --git a/src/include/replication/walsender.h b/src/include/replication/walsender.h
index 874959e..3a93820 100644
--- a/src/include/replication/walsender.h
+++ b/src/include/replication/walsender.h
@@ -12,7 +12,12 @@
 #ifndef _WALSENDER_H
 #define _WALSENDER_H
 
+#include "postgres.h"
+
+#include <signal.h>
+
 #include "access/xlog.h"
+#include "storage/latch.h"
 #include "storage/spin.h"
 
 /*
@@ -23,6 +28,16 @@ typedef struct WalSnd
 	pid_t		pid;			/* this walsender's process id, or 0 */
 	XLogRecPtr	sentPtr;		/* WAL has been sent up to this point */
 
+	/* XXX
+	 * When a walsender process is signaled, to wake it up to send any
+	 * pending WAL, the sender of the signal should send busy to true.
+	 * A walsender marked as busy should not be signaled again, to avoid
+	 * redundant signaling which would slow down the walsender and the
+	 * system as a whole. Walsender will clear the flag when it is
+	 * finished sending all pending WAL again.
+	 */
+	Latch		latch;
+
 	slock_t		mutex;			/* locks shared variables shown above */
 } WalSnd;
 
@@ -45,5 +60,6 @@ extern int	WalSenderMain(void);
 extern void WalSndSignals(void);
 extern Size WalSndShmemSize(void);
 extern void WalSndShmemInit(void);
+extern void WalSndWakeup(void);
 
 #endif   /* _WALSENDER_H */
diff --git a/src/include/storage/latch.h b/src/include/storage/latch.h
new file mode 100644
index 0000000..28989e5
--- /dev/null
+++ b/src/include/storage/latch.h
@@ -0,0 +1,38 @@
+/*-------------------------------------------------------------------------
+ *
+ * latch.h
+ *	  Routines for interprocess latches
+ *
+ *
+ * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * $PostgreSQL$
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef LATCH_H
+#define LATCH_H
+
+typedef struct
+{
+	volatile sig_atomic_t	is_set;
+	volatile sig_atomic_t	owner_pid;
+} Latch;
+
+/*
+ * prototypes for functions in latch.c
+ */
+extern void InitLatch(Latch *latch);
+extern void InitSharedLatch(Latch *latch);
+extern void ReleaseLatch(Latch *latch);
+extern void WaitLatch(Latch *latch, long timeout);
+extern void SetLatch(Latch *latch);
+extern void ResetLatch(Latch *latch);
+
+extern Size LatchShmemSize(void);
+extern void LatchShmemInit(void);
+
+extern void latch_sigusr1_handler(void);
+
+#endif   /* LATCH_H */