TLA  Line data    Source code

       1                 : /*-------------------------------------------------------------------------
       2                 :  *
       3                 :  * pgsleep.c
       4                 :  *     Portable delay handling.
       5                 :  *
       6                 :  *
       7                 :  * Portions Copyright (c) 1996-2023, 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 GIC        5748 : pg_usleep(long microsec)
      42 ECB             : {
      43 CBC        5748 :     if (microsec > 0)
      44 ECB             :     {
      45                 : #ifndef WIN32
      46                 :         struct timespec delay;
      47                 : 
      48 GIC        5748 :         delay.tv_sec = microsec / 1000000L;
      49 GNC        5748 :         delay.tv_nsec = (microsec % 1000000L) * 1000;
      50            5748 :         (void) nanosleep(&delay, NULL);
      51                 : #else
      52                 :         SleepEx((microsec < 500 ? 1 : (microsec + 500) / 1000), FALSE);
      53                 : #endif
      54                 :     }
      55 GIC        5748 : }
      56                 : 
      57                 : #endif                          /* defined(FRONTEND) || !defined(WIN32) */