1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
|
/* Low-level locking access to futex facilities. Stub version.
Copyright (C) 2014-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library. If not, see
<https://www.gnu.org/licenses/>. */
#ifndef _LOWLEVELLOCK_FUTEX_H
#define _LOWLEVELLOCK_FUTEX_H 1
#ifndef __ASSEMBLER__
# include <sysdep.h>
# include <sysdep-cancel.h>
# include <kernel-features.h>
#endif
#define FUTEX_WAIT 0
#define FUTEX_WAKE 1
#define FUTEX_REQUEUE 3
#define FUTEX_CMP_REQUEUE 4
#define FUTEX_WAKE_OP 5
#define FUTEX_OP_CLEAR_WAKE_IF_GT_ONE ((4 << 24) | 1)
#define FUTEX_LOCK_PI 6
#define FUTEX_UNLOCK_PI 7
#define FUTEX_TRYLOCK_PI 8
#define FUTEX_WAIT_BITSET 9
#define FUTEX_WAKE_BITSET 10
#define FUTEX_WAIT_REQUEUE_PI 11
#define FUTEX_CMP_REQUEUE_PI 12
#define FUTEX_PRIVATE_FLAG 128
#define FUTEX_CLOCK_REALTIME 256
#define FUTEX_BITSET_MATCH_ANY 0xffffffff
/* Values for 'private' parameter of locking macros. Yes, the
definition seems to be backwards. But it is not. The bit will be
reversed before passing to the system call. */
#define LLL_PRIVATE 0
#define LLL_SHARED FUTEX_PRIVATE_FLAG
#ifndef __ASSEMBLER__
# if IS_IN (libc) || IS_IN (rtld)
/* In libc.so or ld.so all futexes are private. */
# define __lll_private_flag(fl, private) \
({ \
/* Prevent warnings in callers of this macro. */ \
int __lll_private_flag_priv __attribute__ ((unused)); \
__lll_private_flag_priv = (private); \
((fl) | FUTEX_PRIVATE_FLAG); \
})
# else
# define __lll_private_flag(fl, private) \
(((fl) | FUTEX_PRIVATE_FLAG) ^ (private))
# endif
# define lll_futex_syscall(nargs, futexp, op, ...) \
({ \
INTERNAL_SYSCALL_DECL (__err); \
long int __ret = INTERNAL_SYSCALL (futex, __err, nargs, futexp, op, \
__VA_ARGS__); \
(__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (__ret, __err)) \
? -INTERNAL_SYSCALL_ERRNO (__ret, __err) : 0); \
})
/* For most of these macros, the return value is never really used.
Nevertheless, the protocol is that each one returns a negated errno
code for failure or zero for success. (Note that the corresponding
Linux system calls can sometimes return positive values for success
cases too. We never use those values.) */
/* Wait while *FUTEXP == VAL for an lll_futex_wake call on FUTEXP. */
# define lll_futex_wait(futexp, val, private) \
lll_futex_timed_wait (futexp, val, NULL, private)
# define lll_futex_timed_wait(futexp, val, timeout, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_WAIT, private), \
val, timeout)
/* Verify whether the supplied clockid is supported by
lll_futex_clock_wait_bitset. */
# define lll_futex_supported_clockid(clockid) \
((clockid) == CLOCK_REALTIME || (clockid) == CLOCK_MONOTONIC)
/* The kernel currently only supports CLOCK_MONOTONIC or
CLOCK_REALTIME timeouts for FUTEX_WAIT_BITSET. We could attempt to
convert others here but currently do not. */
# define lll_futex_clock_wait_bitset(futexp, val, clockid, timeout, private) \
({ \
long int __ret; \
if (lll_futex_supported_clockid (clockid)) \
{ \
const unsigned int clockbit = \
(clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0; \
const int op = \
__lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private); \
\
__ret = lll_futex_syscall (6, futexp, op, val, \
timeout, NULL /* Unused. */, \
FUTEX_BITSET_MATCH_ANY); \
} \
else \
__ret = -EINVAL; \
__ret; \
})
/* Wake up up to NR waiters on FUTEXP. */
# define lll_futex_wake(futexp, nr, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_WAKE, private), nr, 0)
/* Wake up up to NR_WAKE waiters on FUTEXP. Move up to NR_MOVE of the
rest from waiting on FUTEXP to waiting on MUTEX (a different futex).
Returns non-zero if error happened, zero if success. */
# define lll_futex_requeue(futexp, nr_wake, nr_move, mutex, val, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_CMP_REQUEUE, private), \
nr_wake, nr_move, mutex, val)
/* Wake up up to NR_WAKE waiters on FUTEXP and NR_WAKE2 on FUTEXP2.
Returns non-zero if error happened, zero if success. */
# define lll_futex_wake_unlock(futexp, nr_wake, nr_wake2, futexp2, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_WAKE_OP, private), \
nr_wake, nr_wake2, futexp2, \
FUTEX_OP_CLEAR_WAKE_IF_GT_ONE)
/* Priority Inheritance support. */
#define lll_futex_timed_lock_pi(futexp, abstime, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_LOCK_PI, private), \
0, abstime)
#define lll_futex_timed_unlock_pi(futexp, private) \
lll_futex_syscall (4, futexp, \
__lll_private_flag (FUTEX_UNLOCK_PI, private), \
0, 0)
/* Like lll_futex_wait (FUTEXP, VAL, PRIVATE) but with the expectation
that lll_futex_cmp_requeue_pi (FUTEXP, _, _, MUTEX, _, PRIVATE) will
be used to do the wakeup. Confers priority-inheritance behavior on
the waiter. */
# define lll_futex_wait_requeue_pi(futexp, val, mutex, private) \
lll_futex_timed_wait_requeue_pi (futexp, val, NULL, 0, mutex, private)
/* Like lll_futex_wait_requeue_pi, but with a timeout. */
# define lll_futex_timed_wait_requeue_pi(futexp, val, timeout, clockbit, \
mutex, private) \
lll_futex_syscall (5, futexp, \
__lll_private_flag (FUTEX_WAIT_REQUEUE_PI \
| (clockbit), private), \
val, timeout, mutex)
/* Like lll_futex_requeue, but pairs with lll_futex_wait_requeue_pi
and inherits priority from the waiter. */
# define lll_futex_cmp_requeue_pi(futexp, nr_wake, nr_move, mutex, \
val, private) \
lll_futex_syscall (6, futexp, \
__lll_private_flag (FUTEX_CMP_REQUEUE_PI, \
private), \
nr_wake, nr_move, mutex, val)
/* Like lll_futex_wait, but acting as a cancellable entrypoint. */
# define lll_futex_wait_cancel(futexp, val, private) \
({ \
int __oldtype = CANCEL_ASYNC (); \
long int __err = lll_futex_wait (futexp, val, LLL_SHARED); \
CANCEL_RESET (__oldtype); \
__err; \
})
/* Like lll_futex_timed_wait, but acting as a cancellable entrypoint. */
# define lll_futex_timed_wait_cancel(futexp, val, timeout, private) \
({ \
int __oldtype = CANCEL_ASYNC (); \
long int __err = lll_futex_timed_wait (futexp, val, timeout, private); \
CANCEL_RESET (__oldtype); \
__err; \
})
#endif /* !__ASSEMBLER__ */
#endif /* lowlevellock-futex.h */
|
