1/* Low-level locking access to futex facilities. Linux version.
2 Copyright (C) 2005-2019 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 _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_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
54#if IS_IN (libc) || IS_IN (rtld)
55/* In libc.so or ld.so all futexes are private. */
56# define __lll_private_flag(fl, private) \
57 ({ \
58 /* Prevent warnings in callers of this macro. */ \
59 int __lll_private_flag_priv __attribute__ ((unused)); \
60 __lll_private_flag_priv = (private); \
61 ((fl) | FUTEX_PRIVATE_FLAG); \
62 })
63#else
64# define __lll_private_flag(fl, private) \
65 (((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
66#endif
67
68#define lll_futex_syscall(nargs, futexp, op, ...) \
69 ({ \
70 INTERNAL_SYSCALL_DECL (__err); \
71 long int __ret = INTERNAL_SYSCALL (futex, __err, nargs, futexp, op, \
72 __VA_ARGS__); \
73 (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret, __err)) \
74 ? -INTERNAL_SYSCALL_ERRNO (__ret, __err) : 0); \
75 })
76
77#define lll_futex_wait(futexp, val, private) \
78 lll_futex_timed_wait (futexp, val, NULL, private)
79
80#define lll_futex_timed_wait(futexp, val, timeout, private) \
81 lll_futex_syscall (4, futexp, \
82 __lll_private_flag (FUTEX_WAIT, private), \
83 val, timeout)
84
85/* Verify whether the supplied clockid is supported by
86 lll_futex_clock_wait_bitset. */
87#define lll_futex_supported_clockid(clockid) \
88 ((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
89
90/* The kernel currently only supports CLOCK_MONOTONIC or
91 CLOCK_REALTIME timeouts for FUTEX_WAIT_BITSET. We could attempt to
92 convert others here but currently do not. */
93#define lll_futex_clock_wait_bitset(futexp, val, clockid, timeout, private) \
94 ({ \
95 long int __ret; \
96 if (lll_futex_supported_clockid (clockid)) \
97 { \
98 const unsigned int clockbit = \
99 (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0; \
100 const int op = \
101 __lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private); \
102 \
103 __ret = lll_futex_syscall (6, futexp, op, val, \
104 timeout, NULL /* Unused. */, \
105 FUTEX_BITSET_MATCH_ANY); \
106 } \
107 else \
108 __ret = -EINVAL; \
109 __ret; \
110 })
111
112#define lll_futex_wake(futexp, nr, private) \
113 lll_futex_syscall (4, futexp, \
114 __lll_private_flag (FUTEX_WAKE, private), nr, 0)
115
116/* Returns non-zero if error happened, zero if success. */
117#define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
118 lll_futex_syscall (6, futexp, \
119 __lll_private_flag (FUTEX_CMP_REQUEUE, private), \
120 nr_wake, nr_move, mutex, val)
121
122/* Returns non-zero if error happened, zero if success. */
123#define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
124 lll_futex_syscall (6, futexp, \
125 __lll_private_flag (FUTEX_WAKE_OP, private), \
126 nr_wake, nr_wake2, futexp2, \
127 FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
128
129/* Priority Inheritance support. */
130#define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
131 lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)
132
133#define lll_futex_timed_wait_requeue_pi(futexp, val, timeout, clockbit, \
134 mutex, private) \
135 lll_futex_syscall (5, futexp, \
136 __lll_private_flag (FUTEX_WAIT_REQUEUE_PI \
137 | (clockbit), private), \
138 val, timeout, mutex)
139
140
141#define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, \
142 val, private) \
143 lll_futex_syscall (6, futexp, \
144 __lll_private_flag (FUTEX_CMP_REQUEUE_PI, \
145 private), \
146 nr_wake, nr_move, mutex, val)
147
148
149/* Cancellable futex macros. */
150#define lll_futex_wait_cancel(futexp, val, private) \
151 ({ \
152 int __oldtype = CANCEL_ASYNC (); \
153 long int __err = lll_futex_wait (futexp, val, LLL_SHARED); \
154 CANCEL_RESET (__oldtype); \
155 __err; \
156 })
157
158#define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
159 ({ \
160 int __oldtype = CANCEL_ASYNC (); \
161 long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
162 CANCEL_RESET (__oldtype); \
163 __err; \
164 })
165
166#endif /* !__ASSEMBLER__ */
167
168#endif /* lowlevellock-futex.h */
169