sysdeps/nacl/lll_timedwait_tid.c

   1 /* Timed waiting for thread death.  NaCl version.
   2    Copyright (C) 2015-2016 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library 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 GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <atomic.h>
  21 #include <errno.h>
  22 #include <lowlevellock.h>
  23 #include <sys/time.h>
  24
  25 int
  26 __lll_timedwait_tid (int *tidp, const struct timespec *abstime)
  27 {
  28   /* Reject invalid timeouts.  */
  29   if (__glibc_unlikely (abstime->tv_nsec < 0)
  30       || __glibc_unlikely (abstime->tv_nsec >= 1000000000))
  31     return EINVAL;
  32
  33   /* Repeat until thread terminated.  */
  34   int tid;
  35   while ((tid = atomic_load_relaxed (tidp)) != 0)
  36     {
  37       /* See exit-thread.h for details.  */
  38       if (tid == NACL_EXITING_TID)
  39         /* The thread should now be in the process of exiting, so it will
  40            finish quick enough that the timeout doesn't matter.  If any
  41            thread ever stays in this state for long, there is something
  42            catastrophically wrong.  */
  43         atomic_spin_nop ();
  44       else
  45         {
  46           assert (tid > 0);
  47
  48           /* If *FUTEX == TID, wait until woken or timeout.  */
  49           int err = __nacl_irt_futex.futex_wait_abs ((volatile int *) tidp,
  50                                                      tid, abstime);
  51           if (err != 0)
  52             {
  53               if (__glibc_likely (err == ETIMEDOUT))
  54                 return err;
  55               assert (err == EAGAIN);
  56             }
  57         }
  58     }
  59
  60   return 0;
  61 }