src/backend/port/win32/timer.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * timer.c
   4  *        Microsoft Windows Win32 Timer Implementation
   5  *
   6  *        Limitations of this implementation:
   7  *
   8  *        - Does not support interval timer (value->it_interval)
   9  *        - Only supports ITIMER_REAL
  10  *
  11  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  12  *
  13  * IDENTIFICATION
  14  *        $PostgreSQL$
  15  *
  16  *-------------------------------------------------------------------------
  17  */
  18
  19 #include "postgres.h"
  20
  21 #include "libpq/pqsignal.h"
  22
  23
  24 /* Communication area for inter-thread communication */
  25 typedef struct timerCA
  26 {
  27         struct itimerval value;
  28         HANDLE          event;
  29         CRITICAL_SECTION crit_sec;
  30 }       timerCA;
  31
  32 static timerCA timerCommArea;
  33 static HANDLE timerThreadHandle = INVALID_HANDLE_VALUE;
  34
  35
  36 /* Timer management thread */
  37 static DWORD WINAPI
  38 pg_timer_thread(LPVOID param)
  39 {
  40         DWORD           waittime;
  41
  42         Assert(param == NULL);
  43
  44         waittime = INFINITE;
  45
  46         for (;;)
  47         {
  48                 int                     r;
  49
  50                 r = WaitForSingleObjectEx(timerCommArea.event, waittime, FALSE);
  51                 if (r == WAIT_OBJECT_0)
  52                 {
  53                         /* Event signalled from main thread, change the timer */
  54                         EnterCriticalSection(&timerCommArea.crit_sec);
  55                         if (timerCommArea.value.it_value.tv_sec == 0 &&
  56                                 timerCommArea.value.it_value.tv_usec == 0)
  57                                 waittime = INFINITE;    /* Cancel the interrupt */
  58                         else
  59                         {
  60                                 /* WaitForSingleObjectEx() uses milliseconds, round up */
  61                                 waittime = (timerCommArea.value.it_value.tv_usec + 999) / 1000 +
  62                                         timerCommArea.value.it_value.tv_sec * 1000;
  63                         }
  64                         ResetEvent(timerCommArea.event);
  65                         LeaveCriticalSection(&timerCommArea.crit_sec);
  66                 }
  67                 else if (r == WAIT_TIMEOUT)
  68                 {
  69                         /* Timeout expired, signal SIGALRM and turn it off */
  70                         pg_queue_signal(SIGALRM);
  71                         waittime = INFINITE;
  72                 }
  73                 else
  74                 {
  75                         /* Should never happen */
  76                         Assert(false);
  77                 }
  78         }
  79
  80         return 0;
  81 }
  82
  83 /*
  84  * Win32 setitimer emulation by creating a persistent thread
  85  * to handle the timer setting and notification upon timeout.
  86  */
  87 int
  88 setitimer(int which, const struct itimerval * value, struct itimerval * ovalue)
  89 {
  90         Assert(value != NULL);
  91         Assert(value->it_interval.tv_sec == 0 && value->it_interval.tv_usec == 0);
  92         Assert(which == ITIMER_REAL);
  93
  94         if (timerThreadHandle == INVALID_HANDLE_VALUE)
  95         {
  96                 /* First call in this backend, create event and the timer thread */
  97                 timerCommArea.event = CreateEvent(NULL, TRUE, FALSE, NULL);
  98                 if (timerCommArea.event == NULL)
  99                         ereport(FATAL,
 100                                         (errmsg_internal("failed to create timer event: %d",
 101                                                                          (int) GetLastError())));
 102
 103                 MemSet(&timerCommArea.value, 0, sizeof(struct itimerval));
 104
 105                 InitializeCriticalSection(&timerCommArea.crit_sec);
 106
 107                 timerThreadHandle = CreateThread(NULL, 0, pg_timer_thread, NULL, 0, NULL);
 108                 if (timerThreadHandle == INVALID_HANDLE_VALUE)
 109                         ereport(FATAL,
 110                                         (errmsg_internal("failed to create timer thread: %d",
 111                                                                          (int) GetLastError())));
 112         }
 113
 114         /* Request the timer thread to change settings */
 115         EnterCriticalSection(&timerCommArea.crit_sec);
 116         if (ovalue)
 117                 *ovalue = timerCommArea.value;
 118         timerCommArea.value = *value;
 119         LeaveCriticalSection(&timerCommArea.crit_sec);
 120         SetEvent(timerCommArea.event);
 121
 122         return 0;
 123 }