1#ifndef _LINUX_FUTEX_H
2#define _LINUX_FUTEX_H
3
4
5#include <linux/types.h>
6
7/* Second argument to futex syscall */
8
9
10#define FUTEX_WAIT 0
11#define FUTEX_WAKE 1
12#define FUTEX_FD 2
13#define FUTEX_REQUEUE 3
14#define FUTEX_CMP_REQUEUE 4
15#define FUTEX_WAKE_OP 5
16#define FUTEX_LOCK_PI 6
17#define FUTEX_UNLOCK_PI 7
18#define FUTEX_TRYLOCK_PI 8
19#define FUTEX_WAIT_BITSET 9
20#define FUTEX_WAKE_BITSET 10
21#define FUTEX_WAIT_REQUEUE_PI 11
22#define FUTEX_CMP_REQUEUE_PI 12
23
24#define FUTEX_PRIVATE_FLAG 128
25#define FUTEX_CLOCK_REALTIME 256
26#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
27
28#define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
29#define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
30#define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
31#define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
32#define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
33#define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
34#define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
35#define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
36#define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG)
37#define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG)
38#define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \
39 FUTEX_PRIVATE_FLAG)
40#define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \
41 FUTEX_PRIVATE_FLAG)
42
43/*
44 * Support for robust futexes: the kernel cleans up held futexes at
45 * thread exit time.
46 */
47
48/*
49 * Per-lock list entry - embedded in user-space locks, somewhere close
50 * to the futex field. (Note: user-space uses a double-linked list to
51 * achieve O(1) list add and remove, but the kernel only needs to know
52 * about the forward link)
53 *
54 * NOTE: this structure is part of the syscall ABI, and must not be
55 * changed.
56 */
57struct robust_list {
58 struct robust_list *next;
59};
60
61/*
62 * Per-thread list head:
63 *
64 * NOTE: this structure is part of the syscall ABI, and must only be
65 * changed if the change is first communicated with the glibc folks.
66 * (When an incompatible change is done, we'll increase the structure
67 * size, which glibc will detect)
68 */
69struct robust_list_head {
70 /*
71 * The head of the list. Points back to itself if empty:
72 */
73 struct robust_list list;
74
75 /*
76 * This relative offset is set by user-space, it gives the kernel
77 * the relative position of the futex field to examine. This way
78 * we keep userspace flexible, to freely shape its data-structure,
79 * without hardcoding any particular offset into the kernel:
80 */
81 long futex_offset;
82
83 /*
84 * The death of the thread may race with userspace setting
85 * up a lock's links. So to handle this race, userspace first
86 * sets this field to the address of the to-be-taken lock,
87 * then does the lock acquire, and then adds itself to the
88 * list, and then clears this field. Hence the kernel will
89 * always have full knowledge of all locks that the thread
90 * _might_ have taken. We check the owner TID in any case,
91 * so only truly owned locks will be handled.
92 */
93 struct robust_list *list_op_pending;
94};
95
96/*
97 * Are there any waiters for this robust futex:
98 */
99#define FUTEX_WAITERS 0x80000000
100
101/*
102 * The kernel signals via this bit that a thread holding a futex
103 * has exited without unlocking the futex. The kernel also does
104 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
105 * up any possible waiters:
106 */
107#define FUTEX_OWNER_DIED 0x40000000
108
109/*
110 * The rest of the robust-futex field is for the TID:
111 */
112#define FUTEX_TID_MASK 0x3fffffff
113
114/*
115 * This limit protects against a deliberately circular list.
116 * (Not worth introducing an rlimit for it)
117 */
118#define ROBUST_LIST_LIMIT 2048
119
120/*
121 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
122 * match of any bit.
123 */
124#define FUTEX_BITSET_MATCH_ANY 0xffffffff
125
126
127#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
128#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
129#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
130#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
131#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
132
133#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
134
135#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
136#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
137#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
138#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
139#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
140#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
141
142/* FUTEX_WAKE_OP will perform atomically
143 int oldval = *(int *)UADDR2;
144 *(int *)UADDR2 = oldval OP OPARG;
145 if (oldval CMP CMPARG)
146 wake UADDR2; */
147
148#define FUTEX_OP(op, oparg, cmp, cmparg) \
149 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
150 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
151
152#endif /* _LINUX_FUTEX_H */
153