4 #include <linux/sched.h>
8 /* Second argument to futex syscall */
14 #define FUTEX_REQUEUE 3
15 #define FUTEX_CMP_REQUEUE 4
16 #define FUTEX_WAKE_OP 5
17 #define FUTEX_LOCK_PI 6
18 #define FUTEX_UNLOCK_PI 7
19 #define FUTEX_TRYLOCK_PI 8
20 #define FUTEX_CMP_REQUEUE_PI 9
23 * Support for robust futexes: the kernel cleans up held futexes at
28 * Per-lock list entry - embedded in user-space locks, somewhere close
29 * to the futex field. (Note: user-space uses a double-linked list to
30 * achieve O(1) list add and remove, but the kernel only needs to know
31 * about the forward link)
33 * NOTE: this structure is part of the syscall ABI, and must not be
37 struct robust_list __user *next;
41 * Per-thread list head:
43 * NOTE: this structure is part of the syscall ABI, and must only be
44 * changed if the change is first communicated with the glibc folks.
45 * (When an incompatible change is done, we'll increase the structure
46 * size, which glibc will detect)
48 struct robust_list_head {
50 * The head of the list. Points back to itself if empty:
52 struct robust_list list;
55 * This relative offset is set by user-space, it gives the kernel
56 * the relative position of the futex field to examine. This way
57 * we keep userspace flexible, to freely shape its data-structure,
58 * without hardcoding any particular offset into the kernel:
63 * The death of the thread may race with userspace setting
64 * up a lock's links. So to handle this race, userspace first
65 * sets this field to the address of the to-be-taken lock,
66 * then does the lock acquire, and then adds itself to the
67 * list, and then clears this field. Hence the kernel will
68 * always have full knowledge of all locks that the thread
69 * _might_ have taken. We check the owner TID in any case,
70 * so only truly owned locks will be handled.
72 struct robust_list __user *list_op_pending;
76 * Are there any waiters for this robust futex:
78 #define FUTEX_WAITERS 0x80000000
81 * The kernel signals via this bit that a thread holding a futex
82 * has exited without unlocking the futex. The kernel also does
83 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
84 * up any possible waiters:
86 #define FUTEX_OWNER_DIED 0x40000000
89 * Some processes have been requeued on this PI-futex
91 #define FUTEX_WAITER_REQUEUED 0x20000000
94 * The rest of the robust-futex field is for the TID:
96 #define FUTEX_TID_MASK 0x0fffffff
99 * This limit protects against a deliberately circular list.
100 * (Not worth introducing an rlimit for it)
102 #define ROBUST_LIST_LIMIT 2048
105 long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
106 u32 __user *uaddr2, u32 val2, u32 val3);
109 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
112 * Futexes are matched on equal values of this key.
113 * The key type depends on whether it's a shared or private mapping.
114 * Don't rearrange members without looking at hash_futex().
116 * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
117 * We set bit 0 to indicate if it's an inode-based key.
127 unsigned long address;
128 struct mm_struct *mm;
137 int get_futex_key(u32 __user *uaddr, union futex_key *key);
138 void get_futex_key_refs(union futex_key *key);
139 void drop_futex_key_refs(union futex_key *key);
142 extern void exit_robust_list(struct task_struct *curr);
143 extern void exit_pi_state_list(struct task_struct *curr);
145 static inline void exit_robust_list(struct task_struct *curr)
148 static inline void exit_pi_state_list(struct task_struct *curr)
152 #endif /* __KERNEL__ */
154 #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */
155 #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */
156 #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */
157 #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */
158 #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */
160 #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */
162 #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */
163 #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */
164 #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */
165 #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */
166 #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */
167 #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */
169 /* FUTEX_WAKE_OP will perform atomically
170 int oldval = *(int *)UADDR2;
171 *(int *)UADDR2 = oldval OP OPARG;
172 if (oldval CMP CMPARG)
175 #define FUTEX_OP(op, oparg, cmp, cmparg) \
176 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \
177 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))