lib/xnanosleep.c

   1 /* xnanosleep.c -- a more convenient interface to nanosleep
   2
   3    Copyright (C) 2002-2007, 2009-2020 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  17
  18 /* Mostly written (for sleep.c) by Paul Eggert.
  19    Factored out (creating this file) by Jim Meyering.  */
  20
  21 #include <config.h>
  22
  23 #include "xnanosleep.h"
  24
  25 #include <intprops.h>
  26 #include <timespec.h>
  27
  28 #include <errno.h>
  29 #include <time.h>
  30 #include <unistd.h>
  31
  32 /* Sleep until the time (call it WAKE_UP_TIME) specified as
  33    SECONDS seconds after the time this function is called.
  34    SECONDS must be non-negative.  If SECONDS is so large that
  35    it is not representable as a 'struct timespec', then use
  36    the maximum value for that interval.  Return -1 on failure
  37    (setting errno), 0 on success.  */
  38
  39 int
  40 xnanosleep (double seconds)
  41 {
  42 #if HAVE_PAUSE
  43   if (1.0 + TYPE_MAXIMUM (time_t) <= seconds)
  44     {
  45       do
  46         pause ();
  47       while (errno == EINTR);
  48
  49       /* pause failed (!); fall back on repeated nanosleep calls.  */
  50     }
  51 #endif
  52
  53   struct timespec ts_sleep = dtotimespec (seconds);
  54
  55   for (;;)
  56     {
  57       /* Linux-2.6.8.1's nanosleep returns -1, but doesn't set errno
  58          when resumed after being suspended.  Earlier versions would
  59          set errno to EINTR.  nanosleep from linux-2.6.10, as well as
  60          implementations by (all?) other vendors, doesn't return -1
  61          in that case;  either it continues sleeping (if time remains)
  62          or it returns zero (if the wake-up time has passed).
  63
  64          Gnulib's replacement nanosleep sometimes does not update
  65          TS_SLEEP, and it is possible some kernels have a similar bug.
  66          However, this merely causes xnanosleep to sleep longer than
  67          necessary, which is not a correctness bug.  */
  68       errno = 0;
  69       if (nanosleep (&ts_sleep, &ts_sleep) == 0)
  70         break;
  71       if (errno != EINTR && errno != 0)
  72         return -1;
  73     }
  74
  75   return 0;
  76 }