1 /*-------------------------------------------------------------------------
2 *
3 * pgsleep.c
4 * Portable delay handling.
5 *
6 *
7 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
8 *
9 * src/port/pgsleep.c
10 *
11 *-------------------------------------------------------------------------
12 */
13 #include "c.h"
14
15 #include <unistd.h>
16 #include <sys/time.h>
17 #ifdef HAVE_SYS_SELECT_H
18 #include <sys/select.h>
19 #endif
20
21 /*
22 * In a Windows backend, we don't use this implementation, but rather
23 * the signal-aware version in src/backend/port/win32/signal.c.
24 */
25 #if defined(FRONTEND) || !defined(WIN32)
26
27 /*
28 * pg_usleep --- delay the specified number of microseconds.
29 *
30 * NOTE: although the delay is specified in microseconds, the effective
31 * resolution is only 1/HZ, or 10 milliseconds, on most Unixen. Expect
32 * the requested delay to be rounded up to the next resolution boundary.
33 *
34 * On machines where "long" is 32 bits, the maximum delay is ~2000 seconds.
35 *
36 * CAUTION: the behavior when a signal arrives during the sleep is platform
37 * dependent. On most Unix-ish platforms, a signal does not terminate the
38 * sleep; but on some, it will (the Windows implementation also allows signals
39 * to terminate pg_usleep). And there are platforms where not only does a
40 * signal not terminate the sleep, but it actually resets the timeout counter
41 * so that the sleep effectively starts over! It is therefore rather hazardous
42 * to use this for long sleeps; a continuing stream of signal events could
43 * prevent the sleep from ever terminating. Better practice for long sleeps
44 * is to use WaitLatch() with a timeout.
45 */
46 void
pg_usleep(long microsec)47 pg_usleep(long microsec)
48 {
49 if (microsec > 0)
50 {
51 #ifndef WIN32
52 struct timeval delay;
53
54 delay.tv_sec = microsec / 1000000L;
55 delay.tv_usec = microsec % 1000000L;
56 (void) select(0, NULL, NULL, NULL, &delay);
57 #else
58 SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
59 #endif
60 }
61 }
62
63 #endif /* defined(FRONTEND) || !defined(WIN32) */
64