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Sourcecode: postgresql-8.4 version File versions

timer.c

/*-------------------------------------------------------------------------
 *
 * 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) 1996-2009, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *      $PostgreSQL: pgsql/src/backend/port/win32/timer.c,v 1.17 2009/06/11 14:49:00 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "libpq/pqsignal.h"


/* 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;


/* 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
                  {
                        /* WaitForSingleObjectEx() uses milliseconds, round up */
                        waittime = (timerCommArea.value.it_value.tv_usec + 999) / 1000 +
                              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;
}

/*
 * 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);
      Assert(value->it_interval.tv_sec == 0 && value->it_interval.tv_usec == 0);
      Assert(which == ITIMER_REAL);

      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.value = *value;
      LeaveCriticalSection(&timerCommArea.crit_sec);
      SetEvent(timerCommArea.event);

      return 0;
}

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