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.

1 files changed, 80 insertions, 33 deletions

diff --git a/src/backend/port/win32/timer.c b/src/backend/port/win32/timer.c
index c31c7bc114e..b6c0b407e6e 100644
--- a/src/backend/port/win32/timer.c
+++ b/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 timerCA timerCommArea;
+static HANDLE timerThreadHandle = INVALID_HANDLE_VALUE;
 
-static VOID CALLBACK
-timer_completion(LPVOID arg, DWORD timeLow, DWORD timeHigh)
+
+/* Timer management thread */
+static DWORD WINAPI
+pg_timer_thread(LPVOID param)
 {
-	pg_queue_signal(SIGALRM);
-}
+	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));
+
+		InitializeCriticalSection(&timerCommArea.crit_sec);
 
-	/* Negative time to SetWaitableTimer means relative time */
-	dueTime.QuadPart = -(value->it_value.tv_usec * 10 + value->it_value.tv_sec * 10000000L);
+		timerThreadHandle = CreateThread(NULL, 0, pg_timer_thread, NULL, 0, NULL);
+		if (timerThreadHandle == INVALID_HANDLE_VALUE)
+			ereport(FATAL,
+					(errmsg_internal("failed to create timer thread: %d",
+									 (int) GetLastError())));
+	}
 
-	/* Turn timer on, or change timer */
-	if (!SetWaitableTimer(timerHandle, &dueTime, 0, timer_completion, NULL, FALSE))
-		ereport(FATAL,
-				(errmsg_internal("failed to set waitable timer: %i", (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;
 }