mach/lowlevellock.h

   1 /* Low-level lock implementation.  Mach gsync-based version.
   2    Copyright (C) 1994-2022 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    <https://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_LOCK_INITIALIZER   0
  36
  37 #define LLL_PRIVATE        0
  38 #define LLL_SHARED         GSYNC_SHARED
  39
  40 /* Interruptible version of __gsync_wait.  */
  41 extern kern_return_t __gsync_wait_intr
  42 (
  43         mach_port_t task,
  44         vm_offset_t addr,
  45         unsigned val1,
  46         unsigned val2,
  47         natural_t msec,
  48         int flags
  49 );
  50
  51 /* Wait on address PTR, without blocking if its contents
  52  * are different from VAL.  */
  53 #define __lll_wait(ptr, val, flags)   \
  54   __gsync_wait (__mach_task_self (),   \
  55     (vm_offset_t)(ptr), (val), 0, 0, (flags))
  56 #define lll_wait(var, val, flags) \
  57   __lll_wait (&(var), val, flags)
  58
  59 /* Interruptible version.  */
  60 #define __lll_wait_intr(ptr, val, flags)   \
  61   __gsync_wait_intr (__mach_task_self (),   \
  62     (vm_offset_t)(ptr), (val), 0, 0, (flags))
  63 #define lll_wait_intr(var, val, flags) \
  64   __lll_wait_intr ((&var), val, flags)
  65
  66 /* Wake one or more threads waiting on address PTR.  */
  67 #define __lll_wake(ptr, flags)   \
  68   __gsync_wake (__mach_task_self (), (vm_offset_t)(ptr), 0, (flags))
  69 #define lll_wake(var, flags) \
  70   __lll_wake (&(var), flags)
  71
  72 /* Acquire the lock at PTR.  */
  73 #define __lll_lock(ptr, flags)   \
  74   ({   \
  75      int *__iptr = (int *)(ptr);   \
  76      int __flags = (flags);   \
  77      if (*__iptr != 0   \
  78          || atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) != 0)   \
  79        while (1)   \
  80          {   \
  81            if (atomic_exchange_acquire (__iptr, 2) == 0)   \
  82              break;   \
  83            __lll_wait (__iptr, 2, __flags);   \
  84          }   \
  85      (void)0;   \
  86    })
  87 #define lll_lock(var, flags) \
  88   __lll_lock (&(var), flags)
  89
  90 /* Try to acquire the lock at PTR, without blocking.
  91    Evaluates to zero on success.  */
  92 #define __lll_trylock(ptr)   \
  93   ({   \
  94      int *__iptr = (int *)(ptr);   \
  95      *__iptr == 0   \
  96        && atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) == 0 ? 0 : -1;   \
  97    })
  98 #define lll_trylock(var) \
  99   __lll_trylock (&(var))
 100
 101 /* Release the lock at PTR.  */
 102 #define __lll_unlock(ptr, flags)   \
 103   ({   \
 104      int *__iptr = (int *)(ptr);   \
 105      if (atomic_exchange_release (__iptr, 0) == 2)   \
 106        __lll_wake (__iptr, (flags));   \
 107      (void)0;   \
 108    })
 109 #define lll_unlock(var, flags) \
 110   __lll_unlock (&(var), flags)
 111
 112 #endif