Re: [PATCHES] Win32 CHECK_FOR_INTERRUPTS() performance

Here is the full patch of the timer implemenation with threading safty
added. Basic test is by several rounds of "make check" and threading
safty test is by a SQL file with many lines of "set statement_timeout =
x". I don't know if there are any corner cases that I should consider, if
any, let me know.

Regards,
Qingqing

---

Index: timer.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/port/win32/timer.c,v
retrieving revision 1.5
diff -c -r1.5 timer.c
*** timer.c 31 Dec 2004 22:00:37 -0000 1.5
--- timer.c 23 Oct 2005 03:04:53 -0000
***************
*** 15,22 ****
--- 15,31 ----

#include "libpq/pqsignal.h"

+ /* Communication area of timer settings */
+ typedef struct timerCA{
+ int which;
+ struct itimerval value;
+ HANDLE event;
+ CRITICAL_SECTION crit_sec;
+ }timerCA;

+ static timerCA timerCommArea;
static HANDLE timerHandle = INVALID_HANDLE_VALUE;
+ static HANDLE timerThreadHandle = INVALID_HANDLE_VALUE;

static VOID CALLBACK
timer_completion(LPVOID arg, DWORD timeLow, DWORD timeHigh)
***************
*** 24,43 ****
pg_queue_signal(SIGALRM);
}

-
/*
* Limitations of this implementation:
*
- * - Does not support setting ovalue
* - Does not support interval timer (value->it_interval)
* - Only supports ITIMER_REAL
*/
! 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);
--- 33,49 ----
pg_queue_signal(SIGALRM);
}

/*
* Limitations of this implementation:
*
* - Does not support interval timer (value->it_interval)
* - Only supports ITIMER_REAL
*/
! static int
! do_setitimer(int which, const struct itimerval * value)
{
LARGE_INTEGER dueTime;

Assert(value != NULL);
Assert(value->it_interval.tv_sec == 0 && value->it_interval.tv_usec == 0);
Assert(which == ITIMER_REAL);
***************
*** 69,71 ****
--- 75,136 ----

return 0;
}
+
+ /* Timer ticking thread */
+ static DWORD WINAPI
+ pg_timer_thread(LPVOID param)
+ {
+ Assert(param == NULL);
+
+ for (;;)
+ {
+ if (WaitForSingleObjectEx(timerCommArea.event, INFINITE, TRUE) == WAIT_OBJECT_0)
+ {
+ EnterCriticalSection(&timerCommArea.crit_sec);
+ do_setitimer(timerCommArea.which,
+ &timerCommArea.value);
+ ResetEvent(timerCommArea.event);
+ LeaveCriticalSection(&timerCommArea.crit_sec);
+ }
+ }
+
+ return 0;
+ }
+
+ /*
+ * 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)
+ {
+ Assert(value != NULL);
+
+ if (timerThreadHandle == INVALID_HANDLE_VALUE)
+ {
+ /* 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 timer event: %d", (int) GetLastError())));
+ MemSet(&timerCommArea.value, 0, sizeof(struct itimerval));
+ InitializeCriticalSection(&timerCommArea.crit_sec);
+
+ 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())));
+ }
+
+ /* Request the timer thread to change settings */
+ EnterCriticalSection(&timerCommArea.crit_sec);
+ if (ovalue)
+ *ovalue = timerCommArea.value;
+ timerCommArea.which = which;
+ timerCommArea.value = *value;
+ LeaveCriticalSection(&timerCommArea.crit_sec);
+ SetEvent(timerCommArea.event);
+
+ /* Timer thread will handle possible errors */
+ return 0;
+ }