sysdeps/nptl/lowlevellock-futex.h

   1 /* Low-level locking access to futex facilities.  Stub version.
   2    Copyright (C) 2014-2024 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 _LOWLEVELLOCK_FUTEX_H
  20 #define _LOWLEVELLOCK_FUTEX_H   1
  21
  22 #ifndef __ASSEMBLER__
  23 # include <sysdep.h>
  24 # include <kernel-features.h>
  25 #endif
  26
  27 #define FUTEX_WAIT              0
  28 #define FUTEX_WAKE              1
  29 #define FUTEX_REQUEUE           3
  30 #define FUTEX_CMP_REQUEUE       4
  31 #define FUTEX_WAKE_OP           5
  32 #define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE   ((4 << 24) | 1)
  33 #define FUTEX_LOCK_PI           6
  34 #define FUTEX_UNLOCK_PI         7
  35 #define FUTEX_TRYLOCK_PI        8
  36 #define FUTEX_WAIT_BITSET       9
  37 #define FUTEX_WAKE_BITSET       10
  38 #define FUTEX_WAIT_REQUEUE_PI   11
  39 #define FUTEX_CMP_REQUEUE_PI    12
  40 #define FUTEX_LOCK_PI2          13
  41 #define FUTEX_PRIVATE_FLAG      128
  42 #define FUTEX_CLOCK_REALTIME    256
  43
  44 #define FUTEX_BITSET_MATCH_ANY  0xffffffff
  45
  46 /* Values for 'private' parameter of locking macros.  Yes, the
  47    definition seems to be backwards.  But it is not.  The bit will be
  48    reversed before passing to the system call.  */
  49 #define LLL_PRIVATE     0
  50 #define LLL_SHARED      FUTEX_PRIVATE_FLAG
  51
  52 #ifndef __ASSEMBLER__
  53 # define __lll_private_flag(fl, private) \
  54   (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
  55
  56 # define lll_futex_syscall(nargs, futexp, op, ...)                      \
  57   ({                                                                    \
  58     long int __ret = INTERNAL_SYSCALL (futex, nargs, futexp, op,        \
  59                                        __VA_ARGS__);                    \
  60     (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret))                \
  61      ? -INTERNAL_SYSCALL_ERRNO (__ret) : 0);                            \
  62   })
  63
  64 /* For most of these macros, the return value is never really used.
  65    Nevertheless, the protocol is that each one returns a negated errno
  66    code for failure or zero for success.  (Note that the corresponding
  67    Linux system calls can sometimes return positive values for success
  68    cases too.  We never use those values.)  */
  69
  70
  71 /* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP.  */
  72 # define lll_futex_wait(futexp, val, private) \
  73   lll_futex_timed_wait (futexp, val, NULL, private)
  74
  75 # define lll_futex_timed_wait(futexp, val, timeout, private)     \
  76   lll_futex_syscall (4, futexp,                                 \
  77                      __lll_private_flag (FUTEX_WAIT, private),  \
  78                      val, timeout)
  79
  80 /* Verify whether the supplied clockid is supported by
  81    lll_futex_clock_wait_bitset.  */
  82 # define lll_futex_supported_clockid(clockid)                   \
  83   ((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
  84
  85 /* Wake up up to NR waiters on FUTEXP.  */
  86 # define lll_futex_wake(futexp, nr, private)                             \
  87   lll_futex_syscall (4, futexp,                                         \
  88                      __lll_private_flag (FUTEX_WAKE, private), nr, 0)
  89
  90 /* Wake up up to NR_WAKE waiters on FUTEXP.  Move up to NR_MOVE of the
  91    rest from waiting on FUTEXP to waiting on MUTEX (a different futex).
  92    Returns non-zero if error happened, zero if success.  */
  93 # define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
  94   lll_futex_syscall (6, futexp,                                         \
  95                      __lll_private_flag (FUTEX_CMP_REQUEUE, private),   \
  96                      nr_wake, nr_move, mutex, val)
  97
  98 /* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.
  99    Returns non-zero if error happened, zero if success.  */
 100 # define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
 101   lll_futex_syscall (6, futexp,                                         \
 102                      __lll_private_flag (FUTEX_WAKE_OP, private),       \
 103                      nr_wake, nr_wake2, futexp2,                        \
 104                      FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
 105
 106
 107 #define lll_futex_timed_unlock_pi(futexp, private)                      \
 108   lll_futex_syscall (4, futexp,                                         \
 109                      __lll_private_flag (FUTEX_UNLOCK_PI, private),     \
 110                      0, 0)
 111
 112 /* Like lll_futex_requeue, but pairs with lll_futex_wait_requeue_pi
 113    and inherits priority from the waiter.  */
 114 # define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex,       \
 115                                  val, private)                          \
 116   lll_futex_syscall (6, futexp,                                         \
 117                      __lll_private_flag (FUTEX_CMP_REQUEUE_PI,          \
 118                                          private),                      \
 119                      nr_wake, nr_move, mutex, val)
 120
 121 /* Like lll_futex_wait, but acting as a cancellable entrypoint.  */
 122 # define lll_futex_wait_cancel(futexp, val, private)                    \
 123   ({                                                                    \
 124      int __op = __lll_private_flag (FUTEX_WAIT, private);               \
 125      INTERNAL_SYSCALL_CANCEL (futex, futexp, __op, val, NULL);          \
 126   })
 127
 128 #endif  /* !__ASSEMBLER__  */
 129
 130 #endif  /* lowlevellock-futex.h */