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/*-------------------------------------------------------------------------
*
* 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) 1996-2021, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/port/win32/timer.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.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 signaled 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("could not create timer event: error code %lu",
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("could not create timer thread: error code %lu",
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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