Line data    Source code

       1              : /*-------------------------------------------------------------------------
       2              :  *
       3              :  * pgsleep.c
       4              :  *     Portable delay handling.
       5              :  *
       6              :  *
       7              :  * Portions Copyright (c) 1996-2026, 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        11257 : pg_usleep(long microsec)
      42              : {
      43        11257 :     if (microsec > 0)
      44              :     {
      45              : #ifndef WIN32
      46              :         struct timespec delay;
      47              : 
      48        11257 :         delay.tv_sec = microsec / 1000000L;
      49        11257 :         delay.tv_nsec = (microsec % 1000000L) * 1000;
      50        11257 :         (void) nanosleep(&delay, NULL);
      51              : #else
      52              :         SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
      53              : #endif
      54              :     }
      55        11257 : }
      56              : 
      57              : #endif                          /* defined(FRONTEND) || !defined(WIN32) */