mach/lowlevellock.h

   1 /* Low-level lock implementation.  Mach gsync-based version.
   2    Copyright (C) 1994-2018 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 _MACH_LOWLEVELLOCK_H
  20 #define _MACH_LOWLEVELLOCK_H   1
  21
  22 #include <mach/gnumach.h>
  23 #include <atomic.h>
  24
  25 /* Gsync flags.  */
  26 #ifndef GSYNC_SHARED
  27   #define GSYNC_SHARED      0x01
  28   #define GSYNC_QUAD        0x02
  29   #define GSYNC_TIMED       0x04
  30   #define GSYNC_BROADCAST   0x08
  31   #define GSYNC_MUTATE      0x10
  32 #endif
  33
  34 /* Static initializer for low-level locks.  */
  35 #define LLL_INITIALIZER   0
  36
  37 /* Wait on address PTR, without blocking if its contents
  38  * are different from VAL.  */
  39 #define lll_wait(ptr, val, flags)   \
  40   __gsync_wait (__mach_task_self (),   \
  41     (vm_offset_t)(ptr), (val), 0, 0, (flags))
  42
  43 /* Wake one or more threads waiting on address PTR.  */
  44 #define lll_wake(ptr, flags)   \
  45   __gsync_wake (__mach_task_self (), (vm_offset_t)(ptr), 0, (flags))
  46
  47 /* Acquire the lock at PTR.  */
  48 #define lll_lock(ptr, flags)   \
  49   ({   \
  50      int *__iptr = (int *)(ptr);   \
  51      int __flags = (flags);   \
  52      if (*__iptr != 0 ||   \
  53          atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) != 0)   \
  54        while (1)   \
  55          {   \
  56            if (atomic_exchange_acq (__iptr, 2) == 0)   \
  57              break;   \
  58            lll_wait (__iptr, 2, __flags);   \
  59          }   \
  60      (void)0;   \
  61    })
  62
  63 /* Try to acquire the lock at PTR, without blocking.
  64    Evaluates to zero on success.  */
  65 #define lll_trylock(ptr)   \
  66   ({   \
  67      int *__iptr = (int *)(ptr);   \
  68      *__iptr == 0 &&   \
  69        atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) == 0 ? 0 : -1;   \
  70    })
  71
  72 /* Release the lock at PTR.  */
  73 #define lll_unlock(ptr, flags)   \
  74   ({   \
  75      int *__iptr = (int *)(ptr);   \
  76      if (atomic_exchange_rel (__iptr, 0) == 2)   \
  77        lll_wake (__iptr, (flags));   \
  78      (void)0;   \
  79    })
  80
  81 #endif