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timer.c
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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) 1996-2025, PostgreSQL Global Development Group
12 *
13 * IDENTIFICATION
14 * src/backend/port/win32/timer.c
15 *
16 *-------------------------------------------------------------------------
17 */
18
19#include "postgres.h"
20
21
22/* Communication area for inter-thread communication */
23typedef struct timerCA
24{
26 HANDLE event;
27 CRITICAL_SECTION crit_sec;
29
31static HANDLE timerThreadHandle = INVALID_HANDLE_VALUE;
32
33
34/* Timer management thread */
35static DWORD WINAPI
36pg_timer_thread(LPVOID param)
37{
38 DWORD waittime;
39
40 Assert(param == NULL);
41
42 waittime = INFINITE;
43
44 for (;;)
45 {
46 int r;
47
48 r = WaitForSingleObjectEx(timerCommArea.event, waittime, FALSE);
49 if (r == WAIT_OBJECT_0)
50 {
51 /* Event signaled from main thread, change the timer */
52 EnterCriticalSection(&timerCommArea.crit_sec);
53 if (timerCommArea.value.it_value.tv_sec == 0 &&
54 timerCommArea.value.it_value.tv_usec == 0)
55 waittime = INFINITE; /* Cancel the interrupt */
56 else
57 {
58 /* WaitForSingleObjectEx() uses milliseconds, round up */
59 waittime = (timerCommArea.value.it_value.tv_usec + 999) / 1000 +
60 timerCommArea.value.it_value.tv_sec * 1000;
61 }
62 ResetEvent(timerCommArea.event);
63 LeaveCriticalSection(&timerCommArea.crit_sec);
64 }
65 else if (r == WAIT_TIMEOUT)
66 {
67 /* Timeout expired, signal SIGALRM and turn it off */
69 waittime = INFINITE;
70 }
71 else
72 {
73 /* Should never happen */
74 Assert(false);
75 }
76 }
77
78 return 0;
79}
80
81/*
82 * Win32 setitimer emulation by creating a persistent thread
83 * to handle the timer setting and notification upon timeout.
84 */
85int
86setitimer(int which, const struct itimerval *value, struct itimerval *ovalue)
87{
88 Assert(value != NULL);
89 Assert(value->it_interval.tv_sec == 0 && value->it_interval.tv_usec == 0);
90 Assert(which == ITIMER_REAL);
91
92 if (timerThreadHandle == INVALID_HANDLE_VALUE)
93 {
94 /* First call in this backend, create event and the timer thread */
95 timerCommArea.event = CreateEvent(NULL, TRUE, FALSE, NULL);
96 if (timerCommArea.event == NULL)
98 (errmsg_internal("could not create timer event: error code %lu",
99 GetLastError())));
100
101 MemSet(&timerCommArea.value, 0, sizeof(struct itimerval));
102
103 InitializeCriticalSection(&timerCommArea.crit_sec);
104
105 timerThreadHandle = CreateThread(NULL, 0, pg_timer_thread, NULL, 0, NULL);
106 if (timerThreadHandle == INVALID_HANDLE_VALUE)
108 (errmsg_internal("could not create timer thread: error code %lu",
109 GetLastError())));
110 }
111
112 /* Request the timer thread to change settings */
113 EnterCriticalSection(&timerCommArea.crit_sec);
114 if (ovalue)
115 *ovalue = timerCommArea.value;
117 LeaveCriticalSection(&timerCommArea.crit_sec);
118 SetEvent(timerCommArea.event);
119
120 return 0;
121}
#define MemSet(start, val, len)
Definition: c.h:991
int errmsg_internal(const char *fmt,...)
Definition: elog.c:1157
#define FATAL
Definition: elog.h:41
#define ereport(elevel,...)
Definition: elog.h:149
Assert(PointerIsAligned(start, uint64))
static struct @165 value
void pg_queue_signal(int signum)
Definition: signal.c:259
struct timeval it_value
Definition: win32_port.h:184
Definition: timer.c:24
CRITICAL_SECTION crit_sec
Definition: timer.c:27
struct itimerval value
Definition: timer.c:25
HANDLE event
Definition: timer.c:26
static timerCA timerCommArea
Definition: timer.c:30
static DWORD WINAPI pg_timer_thread(LPVOID param)
Definition: timer.c:36
struct timerCA timerCA
static HANDLE timerThreadHandle
Definition: timer.c:31
int setitimer(int which, const struct itimerval *value, struct itimerval *ovalue)
Definition: timer.c:86
#define SIGALRM
Definition: win32_port.h:164
#define ITIMER_REAL
Definition: win32_port.h:180