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