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pgsleep.c
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1/*-------------------------------------------------------------------------
2 *
3 * pgsleep.c
4 * Portable delay handling.
5 *
6 *
7 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
8 *
9 * src/port/pgsleep.c
10 *
11 *-------------------------------------------------------------------------
12 */
13#include "c.h"
14
15#include <time.h>
16
17/*
18 * In a Windows backend, we don't use this implementation, but rather
19 * the signal-aware version in src/backend/port/win32/signal.c.
20 */
21#if defined(FRONTEND) || !defined(WIN32)
22
23/*
24 * pg_usleep --- delay the specified number of microseconds.
25 *
26 * NOTE: Although the delay is specified in microseconds, older Unixen and
27 * Windows use periodic kernel ticks to wake up, which might increase the delay
28 * time significantly. We've observed delay increases as large as 20
29 * milliseconds on supported platforms.
30 *
31 * On machines where "long" is 32 bits, the maximum delay is ~2000 seconds.
32 *
33 * CAUTION: It's not a good idea to use long sleeps in the backend. They will
34 * silently return early if a signal is caught, but that doesn't include
35 * latches being set on most OSes, and even signal handlers that set MyLatch
36 * might happen to run before the sleep begins, allowing the full delay.
37 * Better practice is to use WaitLatch() with a timeout, so that backends
38 * respond to latches and signals promptly.
39 */
40void
41pg_usleep(long microsec)
42{
43 if (microsec > 0)
44 {
45#ifndef WIN32
46 struct timespec delay;
47
48 delay.tv_sec = microsec / 1000000L;
49 delay.tv_nsec = (microsec % 1000000L) * 1000;
50 (void) nanosleep(&delay, NULL);
51#else
52 SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
53#endif
54 }
55}
56
57#endif /* defined(FRONTEND) || !defined(WIN32) */
void pg_usleep(long microsec)
Definition: pgsleep.c:41