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) */