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Linus Torvalds1da177e2005-04-16 15:20:36 -07001#ifndef _LINUX_FUTEX_H
2#define _LINUX_FUTEX_H
3
Ingo Molnar0771dfe2006-03-27 01:16:22 -08004#include <linux/sched.h>
5
Linus Torvalds1da177e2005-04-16 15:20:36 -07006/* Second argument to futex syscall */
7
8
Jakub Jelinek4732efb2005-09-06 15:16:25 -07009#define FUTEX_WAIT 0
10#define FUTEX_WAKE 1
11#define FUTEX_FD 2
12#define FUTEX_REQUEUE 3
13#define FUTEX_CMP_REQUEUE 4
14#define FUTEX_WAKE_OP 5
Linus Torvalds1da177e2005-04-16 15:20:36 -070015
Ingo Molnar0771dfe2006-03-27 01:16:22 -080016/*
17 * Support for robust futexes: the kernel cleans up held futexes at
18 * thread exit time.
19 */
20
21/*
22 * Per-lock list entry - embedded in user-space locks, somewhere close
23 * to the futex field. (Note: user-space uses a double-linked list to
24 * achieve O(1) list add and remove, but the kernel only needs to know
25 * about the forward link)
26 *
27 * NOTE: this structure is part of the syscall ABI, and must not be
28 * changed.
29 */
30struct robust_list {
31 struct robust_list __user *next;
32};
33
34/*
35 * Per-thread list head:
36 *
37 * NOTE: this structure is part of the syscall ABI, and must only be
38 * changed if the change is first communicated with the glibc folks.
39 * (When an incompatible change is done, we'll increase the structure
40 * size, which glibc will detect)
41 */
42struct robust_list_head {
43 /*
44 * The head of the list. Points back to itself if empty:
45 */
46 struct robust_list list;
47
48 /*
49 * This relative offset is set by user-space, it gives the kernel
50 * the relative position of the futex field to examine. This way
51 * we keep userspace flexible, to freely shape its data-structure,
52 * without hardcoding any particular offset into the kernel:
53 */
54 long futex_offset;
55
56 /*
57 * The death of the thread may race with userspace setting
58 * up a lock's links. So to handle this race, userspace first
59 * sets this field to the address of the to-be-taken lock,
60 * then does the lock acquire, and then adds itself to the
61 * list, and then clears this field. Hence the kernel will
62 * always have full knowledge of all locks that the thread
63 * _might_ have taken. We check the owner TID in any case,
64 * so only truly owned locks will be handled.
65 */
66 struct robust_list __user *list_op_pending;
67};
68
69/*
70 * Are there any waiters for this robust futex:
71 */
72#define FUTEX_WAITERS 0x80000000
73
74/*
75 * The kernel signals via this bit that a thread holding a futex
76 * has exited without unlocking the futex. The kernel also does
77 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
78 * up any possible waiters:
79 */
80#define FUTEX_OWNER_DIED 0x40000000
81
82/*
Ingo Molnar0771dfe2006-03-27 01:16:22 -080083 * The rest of the robust-futex field is for the TID:
84 */
Ingo Molnar76b81e22006-03-27 01:16:28 -080085#define FUTEX_TID_MASK 0x3fffffff
Ingo Molnar0771dfe2006-03-27 01:16:22 -080086
87/*
Ingo Molnar76b81e22006-03-27 01:16:28 -080088 * This limit protects against a deliberately circular list.
89 * (Not worth introducing an rlimit for it)
Ingo Molnar0771dfe2006-03-27 01:16:22 -080090 */
Ingo Molnar76b81e22006-03-27 01:16:28 -080091#define ROBUST_LIST_LIMIT 2048
Ingo Molnar0771dfe2006-03-27 01:16:22 -080092
Linus Torvalds1da177e2005-04-16 15:20:36 -070093long do_futex(unsigned long uaddr, int op, int val,
94 unsigned long timeout, unsigned long uaddr2, int val2,
95 int val3);
96
Ingo Molnar8f17d3a2006-03-27 01:16:27 -080097extern int handle_futex_death(u32 __user *uaddr, struct task_struct *curr);
Ingo Molnar0771dfe2006-03-27 01:16:22 -080098
99#ifdef CONFIG_FUTEX
100extern void exit_robust_list(struct task_struct *curr);
101#else
102static inline void exit_robust_list(struct task_struct *curr)
103{
104}
105#endif
106
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700107#define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
108#define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
109#define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
110#define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
111#define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
112
113#define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
114
115#define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
116#define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
117#define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
118#define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
119#define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
120#define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
121
122/* FUTEX_WAKE_OP will perform atomically
123 int oldval = *(int *)UADDR2;
124 *(int *)UADDR2 = oldval OP OPARG;
125 if (oldval CMP CMPARG)
126 wake UADDR2; */
127
128#define FUTEX_OP(op, oparg, cmp, cmparg) \
129 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
130 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
131
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132#endif