Split WaitEventSet functions to separate source file

latch.c now only contains the Latch related functions, which build on
the WaitEventSet abstraction. Most of the platform-dependent stuff is
now in waiteventset.c.

Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://www.postgresql.org/message-id/8a507fb6-df28-49d3-81a5-ede180d7f0fb@iki.fi

src/backend/libpq/pqsignal.c

@@ -42,7 +42,7 @@ pqinitmask(void)
 {
 	sigemptyset(&UnBlockSig);
 
-	/* Note: InitializeLatchSupport() modifies UnBlockSig. */
+	/* Note: InitializeWaitEventSupport() modifies UnBlockSig. */
 
 	/* First set all signals, then clear some. */
 	sigfillset(&BlockSig);

src/backend/postmaster/postmaster.c

@@ -548,7 +548,7 @@ PostmasterMain(int argc, char *argv[])
 	pqsignal(SIGCHLD, handle_pm_child_exit_signal);
 
 	/* This may configure SIGURG, depending on platform. */
-	InitializeLatchSupport();
+	InitializeWaitEventSupport();
 	InitProcessLocalLatch();
 
 	/*

src/backend/storage/ipc/Makefile

@@ -25,6 +25,7 @@ OBJS = \
 	signalfuncs.o \
 	sinval.o \
 	sinvaladt.o \
-	standby.o
+	standby.o \
+	waiteventset.o
 
 include $(top_srcdir)/src/backend/common.mk

src/backend/storage/ipc/meson.build

@@ -18,5 +18,6 @@ backend_sources += files(
   'sinval.c',
   'sinvaladt.c',
   'standby.c',
+  'waiteventset.c',
 
 )

src/backend/utils/init/miscinit.c

@@ -127,7 +127,7 @@ InitPostmasterChild(void)
 #endif
 
 	/* Initialize process-local latch support */
-	InitializeLatchSupport();
+	InitializeWaitEventSupport();
 	InitProcessLocalLatch();
 	InitializeLatchWaitSet();
 
@@ -188,7 +188,7 @@ InitStandaloneProcess(const char *argv0)
 	InitProcessGlobals();
 
 	/* Initialize process-local latch support */
-	InitializeLatchSupport();
+	InitializeWaitEventSupport();
 	InitProcessLocalLatch();
 	InitializeLatchWaitSet();
 

src/include/storage/latch.h

@@ -84,10 +84,11 @@
  * use of any generic handler.
  *
  *
- * WaitEventSets allow to wait for latches being set and additional events -
- * postmaster dying and socket readiness of several sockets currently - at the
- * same time.  On many platforms using a long lived event set is more
- * efficient than using WaitLatch or WaitLatchOrSocket.
+ * See also WaitEventSets in waiteventset.h. They allow to wait for latches
+ * being set and additional events - postmaster dying and socket readiness of
+ * several sockets currently - at the same time.  On many platforms using a
+ * long lived event set is more efficient than using WaitLatch or
+ * WaitLatchOrSocket.
  *
  *
  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
@@ -102,7 +103,7 @@
 
 #include <signal.h>
 
-#include "utils/resowner.h"
+#include "storage/waiteventset.h"	/* for WL_* arguments to WaitLatch */
 
 /*
  * Latch structure should be treated as opaque and only accessed through
@@ -120,53 +121,9 @@ typedef struct Latch
 #endif
 } Latch;
 
-/*
- * Bitmasks for events that may wake-up WaitLatch(), WaitLatchOrSocket(), or
- * WaitEventSetWait().
- */
-#define WL_LATCH_SET		 (1 << 0)
-#define WL_SOCKET_READABLE	 (1 << 1)
-#define WL_SOCKET_WRITEABLE  (1 << 2)
-#define WL_TIMEOUT			 (1 << 3)	/* not for WaitEventSetWait() */
-#define WL_POSTMASTER_DEATH  (1 << 4)
-#define WL_EXIT_ON_PM_DEATH	 (1 << 5)
-#ifdef WIN32
-#define WL_SOCKET_CONNECTED  (1 << 6)
-#else
-/* avoid having to deal with case on platforms not requiring it */
-#define WL_SOCKET_CONNECTED  WL_SOCKET_WRITEABLE
-#endif
-#define WL_SOCKET_CLOSED 	 (1 << 7)
-#ifdef WIN32
-#define WL_SOCKET_ACCEPT	 (1 << 8)
-#else
-/* avoid having to deal with case on platforms not requiring it */
-#define WL_SOCKET_ACCEPT	WL_SOCKET_READABLE
-#endif
-#define WL_SOCKET_MASK		(WL_SOCKET_READABLE | \
-							 WL_SOCKET_WRITEABLE | \
-							 WL_SOCKET_CONNECTED | \
-							 WL_SOCKET_ACCEPT | \
-							 WL_SOCKET_CLOSED)
-
-typedef struct WaitEvent
-{
-	int			pos;			/* position in the event data structure */
-	uint32		events;			/* triggered events */
-	pgsocket	fd;				/* socket fd associated with event */
-	void	   *user_data;		/* pointer provided in AddWaitEventToSet */
-#ifdef WIN32
-	bool		reset;			/* Is reset of the event required? */
-#endif
-} WaitEvent;
-
-/* forward declaration to avoid exposing latch.c implementation details */
-typedef struct WaitEventSet WaitEventSet;
-
 /*
  * prototypes for functions in latch.c
  */
-extern void InitializeLatchSupport(void);
 extern void InitLatch(Latch *latch);
 extern void InitSharedLatch(Latch *latch);
 extern void OwnLatch(Latch *latch);
@@ -174,22 +131,10 @@ extern void DisownLatch(Latch *latch);
 extern void SetLatch(Latch *latch);
 extern void ResetLatch(Latch *latch);
 
-extern WaitEventSet *CreateWaitEventSet(ResourceOwner resowner, int nevents);
-extern void FreeWaitEventSet(WaitEventSet *set);
-extern void FreeWaitEventSetAfterFork(WaitEventSet *set);
-extern int	AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd,
-							  Latch *latch, void *user_data);
-extern void ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch);
-
-extern int	WaitEventSetWait(WaitEventSet *set, long timeout,
-							 WaitEvent *occurred_events, int nevents,
-							 uint32 wait_event_info);
 extern int	WaitLatch(Latch *latch, int wakeEvents, long timeout,
 					  uint32 wait_event_info);
 extern int	WaitLatchOrSocket(Latch *latch, int wakeEvents,
 							  pgsocket sock, long timeout, uint32 wait_event_info);
 extern void InitializeLatchWaitSet(void);
-extern int	GetNumRegisteredWaitEvents(WaitEventSet *set);
-extern bool WaitEventSetCanReportClosed(void);
 
 #endif							/* LATCH_H */

src/include/storage/waiteventset.h

@@ -0,0 +1,97 @@
+/*-------------------------------------------------------------------------
+ *
+ * waiteventset.h
+ *		ppoll() / pselect() like interface for waiting for events
+ *
+ * WaitEventSets allow to wait for latches being set and additional events -
+ * postmaster dying and socket readiness of several sockets currently - at the
+ * same time.  On many platforms using a long lived event set is more
+ * efficient than using WaitLatch or WaitLatchOrSocket.
+ *
+ * WaitEventSetWait includes a provision for timeouts (which should be avoided
+ * when possible, as they incur extra overhead) and a provision for postmaster
+ * child processes to wake up immediately on postmaster death.  See
+ * storage/ipc/waiteventset.c for detailed specifications for the exported
+ * functions.
+ *
+ *
+ * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/storage/waiteventset.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef WAITEVENTSET_H
+#define WAITEVENTSET_H
+
+#include "utils/resowner.h"
+
+/*
+ * Bitmasks for events that may wake-up WaitLatch(), WaitLatchOrSocket(), or
+ * WaitEventSetWait().
+ */
+#define WL_LATCH_SET		 (1 << 0)
+#define WL_SOCKET_READABLE	 (1 << 1)
+#define WL_SOCKET_WRITEABLE  (1 << 2)
+#define WL_TIMEOUT			 (1 << 3)	/* not for WaitEventSetWait() */
+#define WL_POSTMASTER_DEATH  (1 << 4)
+#define WL_EXIT_ON_PM_DEATH	 (1 << 5)
+#ifdef WIN32
+#define WL_SOCKET_CONNECTED  (1 << 6)
+#else
+/* avoid having to deal with case on platforms not requiring it */
+#define WL_SOCKET_CONNECTED  WL_SOCKET_WRITEABLE
+#endif
+#define WL_SOCKET_CLOSED 	 (1 << 7)
+#ifdef WIN32
+#define WL_SOCKET_ACCEPT	 (1 << 8)
+#else
+/* avoid having to deal with case on platforms not requiring it */
+#define WL_SOCKET_ACCEPT	WL_SOCKET_READABLE
+#endif
+#define WL_SOCKET_MASK		(WL_SOCKET_READABLE | \
+							 WL_SOCKET_WRITEABLE | \
+							 WL_SOCKET_CONNECTED | \
+							 WL_SOCKET_ACCEPT | \
+							 WL_SOCKET_CLOSED)
+
+typedef struct WaitEvent
+{
+	int			pos;			/* position in the event data structure */
+	uint32		events;			/* triggered events */
+	pgsocket	fd;				/* socket fd associated with event */
+	void	   *user_data;		/* pointer provided in AddWaitEventToSet */
+#ifdef WIN32
+	bool		reset;			/* Is reset of the event required? */
+#endif
+} WaitEvent;
+
+/* forward declarations to avoid exposing waiteventset.c implementation details */
+typedef struct WaitEventSet WaitEventSet;
+
+typedef struct Latch Latch;
+
+/*
+ * prototypes for functions in waiteventset.c
+ */
+extern void InitializeWaitEventSupport(void);
+
+extern WaitEventSet *CreateWaitEventSet(ResourceOwner resowner, int nevents);
+extern void FreeWaitEventSet(WaitEventSet *set);
+extern void FreeWaitEventSetAfterFork(WaitEventSet *set);
+extern int	AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd,
+							  Latch *latch, void *user_data);
+extern void ModifyWaitEvent(WaitEventSet *set, int pos, uint32 events, Latch *latch);
+extern int	WaitEventSetWait(WaitEventSet *set, long timeout,
+							 WaitEvent *occurred_events, int nevents,
+							 uint32 wait_event_info);
+extern int	GetNumRegisteredWaitEvents(WaitEventSet *set);
+extern bool WaitEventSetCanReportClosed(void);
+
+#ifndef WIN32
+extern void WakeupMyProc(void);
+extern void WakeupOtherProc(int pid);
+#endif
+
+#endif							/* WAITEVENTSET_H */