Fix Windows setitimer() emulation to not depend on delivering an APC

to the main thread.  This allows removal of WaitForSingleObjectEx() calls
from the main thread, thereby allowing us to re-enable Qingqing Zhou's
CHECK_FOR_INTERRUPTS performance improvement.  Qingqing, Magnus, et al.

src/backend/port/win32/signal.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/port/win32/signal.c,v 1.13 2005/10/21 21:43:45 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/port/win32/signal.c,v 1.14 2005/10/25 15:15:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -89,16 +89,6 @@ pgwin32_signal_initialize(void)
 				(errmsg_internal("failed to set console control handler")));
 }
 
-/*
- * Support routine for CHECK_FOR_INTERRUPTS() macro
- */
-void
-pgwin32_check_queued_signals(void)
-{
-	if (WaitForSingleObjectEx(pgwin32_signal_event, 0, TRUE) == WAIT_OBJECT_0)
-		pgwin32_dispatch_queued_signals();
-}
-
 /*
  * Dispatch all signals currently queued and not blocked
  * Blocked signals are ignored, and will be fired at the time of

src/backend/port/win32/socket.c

@@ -6,7 +6,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/port/win32/socket.c,v 1.9 2005/10/15 02:49:23 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/port/win32/socket.c,v 1.10 2005/10/25 15:15:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -93,7 +93,7 @@ TranslateSocketError(void)
 static int
 pgwin32_poll_signals(void)
 {
-	if (WaitForSingleObjectEx(pgwin32_signal_event, 0, TRUE) == WAIT_OBJECT_0)
+	if (UNBLOCKED_SIGNAL_QUEUE())
 	{
 		pgwin32_dispatch_queued_signals();
 		errno = EINTR;

src/backend/port/win32/timer.c

@@ -3,10 +3,15 @@
  * timer.c
  *	  Microsoft Windows Win32 Timer Implementation
  *
+ *    Limitations of this implementation:
+ *
+ *    - Does not support interval timer (value->it_interval)
+ *    - Only supports ITIMER_REAL
+ *
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/port/win32/timer.c,v 1.5 2004/12/31 22:00:37 pgsql Exp $
+ *	  $PostgreSQL: pgsql/src/backend/port/win32/timer.c,v 1.6 2005/10/25 15:15:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -16,56 +21,98 @@
 #include "libpq/pqsignal.h"
 
 
-static HANDLE timerHandle = INVALID_HANDLE_VALUE;
+/* Communication area for inter-thread communication */
+typedef struct timerCA {
+	struct itimerval value;
+	HANDLE event;
+	CRITICAL_SECTION crit_sec;
+} timerCA;
 
-static VOID CALLBACK
-timer_completion(LPVOID arg, DWORD timeLow, DWORD timeHigh)
+static timerCA timerCommArea;
+static HANDLE timerThreadHandle = INVALID_HANDLE_VALUE;
+
+
+/* Timer management thread */
+static DWORD WINAPI
+pg_timer_thread(LPVOID param)
 {
+	DWORD waittime;
+
+	Assert(param == NULL);
+
+	waittime = INFINITE;
+
+	for (;;)
+	{
+		int r;
+
+		r = WaitForSingleObjectEx(timerCommArea.event, waittime, FALSE);
+		if (r == WAIT_OBJECT_0)
+		{
+			/* Event signalled from main thread, change the timer */
+			EnterCriticalSection(&timerCommArea.crit_sec);
+			if (timerCommArea.value.it_value.tv_sec == 0 &&
+				timerCommArea.value.it_value.tv_usec == 0)
+				waittime = INFINITE; /* Cancel the interrupt */
+			else
+				waittime = timerCommArea.value.it_value.tv_usec / 10 + timerCommArea.value.it_value.tv_sec * 1000;
+			ResetEvent(timerCommArea.event);
+			LeaveCriticalSection(&timerCommArea.crit_sec);
+		}
+		else if (r == WAIT_TIMEOUT)
+		{
+			/* Timeout expired, signal SIGALRM and turn it off */
 			pg_queue_signal(SIGALRM);
-}
+			waittime = INFINITE;
+		}
+		else
+		{
+			/* Should never happen */
+			Assert(false);
+		}
+	}
 
+	return 0;
+}
 
 /*
- * Limitations of this implementation:
- *
- * - Does not support setting ovalue
- * - Does not support interval timer (value->it_interval)
- * - Only supports ITIMER_REAL
+ * Win32 setitimer emulation by creating a persistent thread
+ * to handle the timer setting and notification upon timeout.
  */
 int
 setitimer(int which, const struct itimerval * value, struct itimerval * ovalue)
 {
-	LARGE_INTEGER dueTime;
-
-	Assert(ovalue == NULL);
 	Assert(value != NULL);
 	Assert(value->it_interval.tv_sec == 0 && value->it_interval.tv_usec == 0);
 	Assert(which == ITIMER_REAL);
 
-	if (timerHandle == INVALID_HANDLE_VALUE)
+	if (timerThreadHandle == INVALID_HANDLE_VALUE)
 	{
-		/* First call in this backend, create new timer object */
-		timerHandle = CreateWaitableTimer(NULL, TRUE, NULL);
-		if (timerHandle == NULL)
+		/* First call in this backend, create event and the timer thread */
+		timerCommArea.event = CreateEvent(NULL, TRUE, FALSE, NULL);
+		if (timerCommArea.event == NULL)
 			ereport(FATAL,
-					(errmsg_internal("failed to create waitable timer: %i", (int) GetLastError())));
-	}
+					(errmsg_internal("failed to create timer event: %d",
+									 (int) GetLastError())));
 
-	if (value->it_value.tv_sec == 0 &&
-		value->it_value.tv_usec == 0)
-	{
-		/* Turn timer off */
-		CancelWaitableTimer(timerHandle);
-		return 0;
-	}
+		MemSet(&timerCommArea.value, 0, sizeof(struct itimerval));
 
-	/* Negative time to SetWaitableTimer means relative time */
-	dueTime.QuadPart = -(value->it_value.tv_usec * 10 + value->it_value.tv_sec * 10000000L);
+		InitializeCriticalSection(&timerCommArea.crit_sec);
 
-	/* Turn timer on, or change timer */
-	if (!SetWaitableTimer(timerHandle, &dueTime, 0, timer_completion, NULL, FALSE))
+		timerThreadHandle = CreateThread(NULL, 0, pg_timer_thread, NULL, 0, NULL);
+		if (timerThreadHandle == INVALID_HANDLE_VALUE)
 			ereport(FATAL,
-				(errmsg_internal("failed to set waitable timer: %i", (int) GetLastError())));
+					(errmsg_internal("failed to create timer thread: %d",
+									 (int) GetLastError())));
+	}
+
+	/* Request the timer thread to change settings */
+	EnterCriticalSection(&timerCommArea.crit_sec);
+	if (ovalue)
+		*ovalue = timerCommArea.value;
+	timerCommArea.value = *value;
+	LeaveCriticalSection(&timerCommArea.crit_sec);
+	SetEvent(timerCommArea.event);
 
 	return 0;
 }

src/include/miscadmin.h

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.182 2005/10/22 17:09:48 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.183 2005/10/25 15:15:16 tgl Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to other files.
@@ -88,7 +88,8 @@ do { \
 
 #define CHECK_FOR_INTERRUPTS() \
 do { \
-	pgwin32_check_queued_signals(); \
+	if (UNBLOCKED_SIGNAL_QUEUE()) \
+		pgwin32_dispatch_queued_signals(); \
 	if (InterruptPending) \
 		ProcessInterrupts(); \
 } while(0)

src/include/port/win32.h

-/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.48 2005/10/21 21:43:46 tgl Exp $ */
+/* $PostgreSQL: pgsql/src/include/port/win32.h,v 1.49 2005/10/25 15:15:16 tgl Exp $ */
 
 /* undefine and redefine after #include */
 #undef mkdir
@@ -224,7 +224,6 @@ extern HANDLE pgwin32_initial_signal_pipe;
 
 void		pgwin32_signal_initialize(void);
 HANDLE		pgwin32_create_signal_listener(pid_t pid);
-void		pgwin32_check_queued_signals(void);
 void		pgwin32_dispatch_queued_signals(void);
 void		pg_queue_signal(int signum);