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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) 1996-2024, 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  */
40 void
41 pg_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