1/* Low-level locking access to futex facilities. Stub version.
2 Copyright (C) 2014-2023 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 <sysdep-cancel.h>
25# include <kernel-features.h>
26#endif
27
28#define FUTEX_WAIT 0
29#define FUTEX_WAKE 1
30#define FUTEX_REQUEUE 3
31#define FUTEX_CMP_REQUEUE 4
32#define FUTEX_WAKE_OP 5
33#define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE ((4 << 24) | 1)
34#define FUTEX_LOCK_PI 6
35#define FUTEX_UNLOCK_PI 7
36#define FUTEX_TRYLOCK_PI 8
37#define FUTEX_WAIT_BITSET 9
38#define FUTEX_WAKE_BITSET 10
39#define FUTEX_WAIT_REQUEUE_PI 11
40#define FUTEX_CMP_REQUEUE_PI 12
41#define FUTEX_LOCK_PI2 13
42#define FUTEX_PRIVATE_FLAG 128
43#define FUTEX_CLOCK_REALTIME 256
44
45#define FUTEX_BITSET_MATCH_ANY 0xffffffff
46
47/* Values for 'private' parameter of locking macros. Yes, the
48 definition seems to be backwards. But it is not. The bit will be
49 reversed before passing to the system call. */
50#define LLL_PRIVATE 0
51#define LLL_SHARED FUTEX_PRIVATE_FLAG
52
53#ifndef __ASSEMBLER__
54# define __lll_private_flag(fl, private) \
55 (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
56
57# define lll_futex_syscall(nargs, futexp, op, ...) \
58 ({ \
59 long int __ret = INTERNAL_SYSCALL (futex, nargs, futexp, op, \
60 __VA_ARGS__); \
61 (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret)) \
62 ? -INTERNAL_SYSCALL_ERRNO (__ret) : 0); \
63 })
64
65/* For most of these macros, the return value is never really used.
66 Nevertheless, the protocol is that each one returns a negated errno
67 code for failure or zero for success. (Note that the corresponding
68 Linux system calls can sometimes return positive values for success
69 cases too. We never use those values.) */
70
71
72/* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP. */
73# define lll_futex_wait(futexp, val, private) \
74 lll_futex_timed_wait (futexp, val, NULL, private)
75
76# define lll_futex_timed_wait(futexp, val, timeout, private) \
77 lll_futex_syscall (4, futexp, \
78 __lll_private_flag (FUTEX_WAIT, private), \
79 val, timeout)
80
81/* Verify whether the supplied clockid is supported by
82 lll_futex_clock_wait_bitset. */
83# define lll_futex_supported_clockid(clockid) \
84 ((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
85
86/* Wake up up to NR waiters on FUTEXP. */
87# define lll_futex_wake(futexp, nr, private) \
88 lll_futex_syscall (4, futexp, \
89 __lll_private_flag (FUTEX_WAKE, private), nr, 0)
90
91/* Wake up up to NR_WAKE waiters on FUTEXP. Move up to NR_MOVE of the
92 rest from waiting on FUTEXP to waiting on MUTEX (a different futex).
93 Returns non-zero if error happened, zero if success. */
94# define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
95 lll_futex_syscall (6, futexp, \
96 __lll_private_flag (FUTEX_CMP_REQUEUE, private), \
97 nr_wake, nr_move, mutex, val)
98
99/* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.
100 Returns non-zero if error happened, zero if success. */
101# define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
102 lll_futex_syscall (6, futexp, \
103 __lll_private_flag (FUTEX_WAKE_OP, private), \
104 nr_wake, nr_wake2, futexp2, \
105 FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
106
107
108#define lll_futex_timed_unlock_pi(futexp, private) \
109 lll_futex_syscall (4, futexp, \
110 __lll_private_flag (FUTEX_UNLOCK_PI, private), \
111 0, 0)
112
113/* Like lll_futex_requeue, but pairs with lll_futex_wait_requeue_pi
114 and inherits priority from the waiter. */
115# define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, \
116 val, private) \
117 lll_futex_syscall (6, futexp, \
118 __lll_private_flag (FUTEX_CMP_REQUEUE_PI, \
119 private), \
120 nr_wake, nr_move, mutex, val)
121
122/* Like lll_futex_wait, but acting as a cancellable entrypoint. */
123# define lll_futex_wait_cancel(futexp, val, private) \
124 ({ \
125 int __oldtype = LIBC_CANCEL_ASYNC (); \
126 long int __err = lll_futex_wait (futexp, val, LLL_SHARED); \
127 LIBC_CANCEL_RESET (__oldtype); \
128 __err; \
129 })
130
131/* Like lll_futex_timed_wait, but acting as a cancellable entrypoint. */
132# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
133 ({ \
134 int __oldtype = LIBC_CANCEL_ASYNC (); \
135 long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
136 LIBC_CANCEL_RESET (__oldtype); \
137 __err; \
138 })
139
140#endif /* !__ASSEMBLER__ */
141
142#endif /* lowlevellock-futex.h */
143