Line data    Source code

       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       10134 : pg_usleep(long microsec)
      42             : {
      43       10134 :     if (microsec > 0)
      44             :     {
      45             : #ifndef WIN32
      46             :         struct timespec delay;
      47             : 
      48       10134 :         delay.tv_sec = microsec / 1000000L;
      49       10134 :         delay.tv_nsec = (microsec % 1000000L) * 1000;
      50       10134 :         (void) nanosleep(&delay, NULL);
      51             : #else
      52             :         SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
      53             : #endif
      54             :     }
      55       10134 : }
      56             : 
      57             : #endif                          /* defined(FRONTEND) || !defined(WIN32) */