Line data Source code
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
47 1272 : pg_usleep(long microsec)
48 : {
49 1272 : if (microsec > 0)
50 : {
51 : #ifndef WIN32
52 : struct timeval delay;
53 :
54 1272 : delay.tv_sec = microsec / 1000000L;
55 1272 : delay.tv_usec = microsec % 1000000L;
56 1272 : (void) select(0, NULL, NULL, NULL, &delay);
57 : #else
58 : SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
59 : #endif
60 : }
61 1271 : }
62 :
63 : #endif /* defined(FRONTEND) || !defined(WIN32) */
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