src/port/pgsleep.c

   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) */