sysdeps/nacl/lowlevellock-futex.h

   1 /* Low-level locking access to futex facilities.  NaCl version.
   2    Copyright (C) 2015 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 #ifndef _LOWLEVELLOCK_FUTEX_H
  20 #define _LOWLEVELLOCK_FUTEX_H   1
  21
  22 #include <nacl-interfaces.h>
  23 #include <time.h>
  24
  25
  26 #pragma GCC diagnostic ignored "-Wunused-value" /* XXX */
  27
  28 /* Values for 'private' parameter of locking macros.  Note pthreadP.h
  29    optimizes for these exact values, though they are not required.  */
  30 #define LLL_PRIVATE     0
  31 #define LLL_SHARED      128
  32
  33 #define FUTEX_PRIVATE_FLAG      0       /* XXX */
  34
  35
  36 /* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP.  */
  37 #define lll_futex_wait(futexp, val, private) \
  38   (- __nacl_irt_futex.futex_wait_abs ((volatile int *) (futexp), val, NULL))
  39
  40 /* Wait until a lll_futex_wake call on FUTEXP, or TIMEOUT elapses.  */
  41 #define lll_futex_timed_wait(futexp, val, timeout, private)             \
  42   ({                                                                    \
  43     /* This timeout is relative, but the IRT call wants it absolute.  */ \
  44     const struct timespec *_to = (timeout);                             \
  45     struct timespec _ts;                                                \
  46     int _err = 0;                                                       \
  47     if (_to != NULL                                                     \
  48         && __glibc_likely ((_err = __nacl_irt_clock.clock_gettime       \
  49                             (CLOCK_REALTIME, &_ts)) == 0))              \
  50       {                                                                 \
  51         _ts.tv_sec -= _to->tv_sec;                                      \
  52         _ts.tv_nsec -= _to->tv_nsec;                                    \
  53         while (_ts.tv_nsec < 0)                                         \
  54           {                                                             \
  55             _ts.tv_nsec += 1000000000;                                  \
  56             --_ts.tv_sec;                                               \
  57           }                                                             \
  58         _to = &_ts;                                                     \
  59       }                                                                 \
  60     if (_err == 0)                                                      \
  61       _err = __nacl_irt_futex.futex_wait_abs                            \
  62         ((volatile int *) (futexp), val, _to);                          \
  63     -_err;                                                              \
  64   })
  65
  66 /* Wake up up to NR waiters on FUTEXP.  */
  67 #define lll_futex_wake(futexp, nr, private)                     \
  68   ({                                                            \
  69     int _woken;                                                 \
  70     - __nacl_irt_futex.futex_wake ((volatile int *) (futexp), nr, &_woken); \
  71   })
  72
  73 /* NaCl does not support the requeue operation.  The only use of this is in
  74    pthread_cond_broadcast, which handles an error return by falling back to
  75    plain lll_futex_wake.  */
  76 #define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
  77   ((futexp), (nr_wake), (nr_move), (mutex), (val), (private), -ENOSYS)
  78
  79 /* NaCl does not support the special wake-unlock operation.  The only use
  80    of this is in pthread_cond_signal, which handles an error return by
  81    falling back to plain lll_futex_wake.  */
  82 /* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.  */
  83 #define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
  84   ((futexp), (nr_wake), (nr_wake2), (futexp2), (private), -ENOSYS)
  85
  86
  87 #endif  /* lowlevellock-futex.h */