mach/lowlevellock.h

   1 /* Low-level lock implementation.  Mach gsync-based version.
   2    Copyright (C) 1994-2024 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.h>
  23 #include <mach/gnumach.h>
  24 #include <atomic.h>
  25
  26 /* Gsync flags.  */
  27 #ifndef GSYNC_SHARED
  28 # define GSYNC_SHARED      0x01
  29 # define GSYNC_QUAD        0x02
  30 # define GSYNC_TIMED       0x04
  31 # define GSYNC_BROADCAST   0x08
  32 # define GSYNC_MUTATE      0x10
  33 #endif
  34
  35 /* Static initializer for low-level locks.  */
  36 #define LLL_LOCK_INITIALIZER   0
  37
  38 #define LLL_PRIVATE        0
  39 #define LLL_SHARED         GSYNC_SHARED
  40
  41 /* Interruptible version of __gsync_wait.  */
  42 extern kern_return_t __gsync_wait_intr
  43 (
  44         mach_port_t task,
  45         vm_offset_t addr,
  46         unsigned val1,
  47         unsigned val2,
  48         natural_t msec,
  49         int flags
  50 );
  51
  52 /* Wait on address PTR, without blocking if its contents
  53  * are different from VAL.  */
  54 #define __lll_wait(ptr, val, flags)   \
  55   __gsync_wait (__mach_task_self (),   \
  56     (vm_offset_t)(ptr), (val), 0, 0, (flags))
  57 #define lll_wait(var, val, flags) \
  58   __lll_wait (&(var), val, flags)
  59
  60 /* Interruptible version.  */
  61 #define __lll_wait_intr(ptr, val, flags)   \
  62   __gsync_wait_intr (__mach_task_self (),   \
  63     (vm_offset_t)(ptr), (val), 0, 0, (flags))
  64 #define lll_wait_intr(var, val, flags) \
  65   __lll_wait_intr ((&var), val, flags)
  66
  67 /* Wake one or more threads waiting on address PTR.  */
  68 #define __lll_wake(ptr, flags)   \
  69   __gsync_wake (__mach_task_self (), (vm_offset_t)(ptr), 0, (flags))
  70 #define lll_wake(var, flags) \
  71   __lll_wake (&(var), flags)
  72
  73 /* Acquire the lock at PTR.  */
  74 #define __lll_lock(ptr, flags)   \
  75   ({   \
  76      int *__iptr = (int *)(ptr);   \
  77      int __flags = (flags);   \
  78      if (*__iptr != 0   \
  79          || atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) != 0)   \
  80        while (1)   \
  81          {   \
  82            if (atomic_exchange_acquire (__iptr, 2) == 0)   \
  83              break;   \
  84            __lll_wait (__iptr, 2, __flags);   \
  85          }   \
  86      (void)0;   \
  87    })
  88 #define lll_lock(var, flags) \
  89   __lll_lock (&(var), flags)
  90
  91 /* Try to acquire the lock at PTR, without blocking.
  92    Evaluates to zero on success.  */
  93 #define __lll_trylock(ptr)   \
  94   ({   \
  95      int *__iptr = (int *)(ptr);   \
  96      *__iptr == 0   \
  97        && atomic_compare_and_exchange_bool_acq (__iptr, 1, 0) == 0 ? 0 : -1;   \
  98    })
  99 #define lll_trylock(var) \
 100   __lll_trylock (&(var))
 101
 102 /* Release the lock at PTR.  */
 103 #define __lll_unlock(ptr, flags)   \
 104   ({   \
 105      int *__iptr = (int *)(ptr);   \
 106      if (atomic_exchange_release (__iptr, 0) == 2)   \
 107        __lll_wake (__iptr, (flags));   \
 108      (void)0;   \
 109    })
 110 #define lll_unlock(var, flags) \
 111   __lll_unlock (&(var), flags)
 112
 113 #endif