futex.h (6126B) - Raw
1 /* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ 2 #ifndef _LINUX_FUTEX_H 3 #define _LINUX_FUTEX_H 4 5 6 #include <linux/types.h> 7 8 /* Second argument to futex syscall */ 9 10 11 #define FUTEX_WAIT 0 12 #define FUTEX_WAKE 1 13 #define FUTEX_FD 2 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_WAIT_BITSET 9 21 #define FUTEX_WAKE_BITSET 10 22 #define FUTEX_WAIT_REQUEUE_PI 11 23 #define FUTEX_CMP_REQUEUE_PI 12 24 #define FUTEX_LOCK_PI2 13 25 26 #define FUTEX_PRIVATE_FLAG 128 27 #define FUTEX_CLOCK_REALTIME 256 28 #define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME) 29 30 #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG) 31 #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG) 32 #define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG) 33 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG) 34 #define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG) 35 #define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG) 36 #define FUTEX_LOCK_PI2_PRIVATE (FUTEX_LOCK_PI2 | FUTEX_PRIVATE_FLAG) 37 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG) 38 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG) 39 #define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG) 40 #define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG) 41 #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ 42 FUTEX_PRIVATE_FLAG) 43 #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ 44 FUTEX_PRIVATE_FLAG) 45 46 /* 47 * Flags for futex2 syscalls. 48 * 49 * NOTE: these are not pure flags, they can also be seen as: 50 * 51 * union { 52 * u32 flags; 53 * struct { 54 * u32 size : 2, 55 * numa : 1, 56 * : 4, 57 * private : 1; 58 * }; 59 * }; 60 */ 61 #define FUTEX2_SIZE_U8 0x00 62 #define FUTEX2_SIZE_U16 0x01 63 #define FUTEX2_SIZE_U32 0x02 64 #define FUTEX2_SIZE_U64 0x03 65 #define FUTEX2_NUMA 0x04 66 /* 0x08 */ 67 /* 0x10 */ 68 /* 0x20 */ 69 /* 0x40 */ 70 #define FUTEX2_PRIVATE FUTEX_PRIVATE_FLAG 71 72 #define FUTEX2_SIZE_MASK 0x03 73 74 /* do not use */ 75 #define FUTEX_32 FUTEX2_SIZE_U32 /* historical accident :-( */ 76 77 /* 78 * Max numbers of elements in a futex_waitv array 79 */ 80 #define FUTEX_WAITV_MAX 128 81 82 /** 83 * struct futex_waitv - A waiter for vectorized wait 84 * @val: Expected value at uaddr 85 * @uaddr: User address to wait on 86 * @flags: Flags for this waiter 87 * @__reserved: Reserved member to preserve data alignment. Should be 0. 88 */ 89 struct futex_waitv { 90 __u64 val; 91 __u64 uaddr; 92 __u32 flags; 93 __u32 __reserved; 94 }; 95 96 /* 97 * Support for robust futexes: the kernel cleans up held futexes at 98 * thread exit time. 99 */ 100 101 /* 102 * Per-lock list entry - embedded in user-space locks, somewhere close 103 * to the futex field. (Note: user-space uses a double-linked list to 104 * achieve O(1) list add and remove, but the kernel only needs to know 105 * about the forward link) 106 * 107 * NOTE: this structure is part of the syscall ABI, and must not be 108 * changed. 109 */ 110 struct robust_list { 111 struct robust_list *next; 112 }; 113 114 /* 115 * Per-thread list head: 116 * 117 * NOTE: this structure is part of the syscall ABI, and must only be 118 * changed if the change is first communicated with the glibc folks. 119 * (When an incompatible change is done, we'll increase the structure 120 * size, which glibc will detect) 121 */ 122 struct robust_list_head { 123 /* 124 * The head of the list. Points back to itself if empty: 125 */ 126 struct robust_list list; 127 128 /* 129 * This relative offset is set by user-space, it gives the kernel 130 * the relative position of the futex field to examine. This way 131 * we keep userspace flexible, to freely shape its data-structure, 132 * without hardcoding any particular offset into the kernel: 133 */ 134 long futex_offset; 135 136 /* 137 * The death of the thread may race with userspace setting 138 * up a lock's links. So to handle this race, userspace first 139 * sets this field to the address of the to-be-taken lock, 140 * then does the lock acquire, and then adds itself to the 141 * list, and then clears this field. Hence the kernel will 142 * always have full knowledge of all locks that the thread 143 * _might_ have taken. We check the owner TID in any case, 144 * so only truly owned locks will be handled. 145 */ 146 struct robust_list *list_op_pending; 147 }; 148 149 /* 150 * Are there any waiters for this robust futex: 151 */ 152 #define FUTEX_WAITERS 0x80000000 153 154 /* 155 * The kernel signals via this bit that a thread holding a futex 156 * has exited without unlocking the futex. The kernel also does 157 * a FUTEX_WAKE on such futexes, after setting the bit, to wake 158 * up any possible waiters: 159 */ 160 #define FUTEX_OWNER_DIED 0x40000000 161 162 /* 163 * The rest of the robust-futex field is for the TID: 164 */ 165 #define FUTEX_TID_MASK 0x3fffffff 166 167 /* 168 * This limit protects against a deliberately circular list. 169 * (Not worth introducing an rlimit for it) 170 */ 171 #define ROBUST_LIST_LIMIT 2048 172 173 /* 174 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a 175 * match of any bit. 176 */ 177 #define FUTEX_BITSET_MATCH_ANY 0xffffffff 178 179 180 #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */ 181 #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */ 182 #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */ 183 #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */ 184 #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */ 185 186 #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */ 187 188 #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */ 189 #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */ 190 #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */ 191 #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */ 192 #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */ 193 #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */ 194 195 /* FUTEX_WAKE_OP will perform atomically 196 int oldval = *(int *)UADDR2; 197 *(int *)UADDR2 = oldval OP OPARG; 198 if (oldval CMP CMPARG) 199 wake UADDR2; */ 200 201 #define FUTEX_OP(op, oparg, cmp, cmparg) \ 202 (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \ 203 | ((oparg & 0xfff) << 12) | (cmparg & 0xfff)) 204 205 #endif /* _LINUX_FUTEX_H */