Edit File: futex.h
/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ #ifndef _LINUX_FUTEX_H #define _LINUX_FUTEX_H #include <linux/types.h> /* Second argument to futex syscall */ #define FUTEX_WAIT 0 #define FUTEX_WAKE 1 #define FUTEX_FD 2 #define FUTEX_REQUEUE 3 #define FUTEX_CMP_REQUEUE 4 #define FUTEX_WAKE_OP 5 #define FUTEX_LOCK_PI 6 #define FUTEX_UNLOCK_PI 7 #define FUTEX_TRYLOCK_PI 8 #define FUTEX_WAIT_BITSET 9 #define FUTEX_WAKE_BITSET 10 #define FUTEX_WAIT_REQUEUE_PI 11 #define FUTEX_CMP_REQUEUE_PI 12 #define FUTEX_PRIVATE_FLAG 128 #define FUTEX_CLOCK_REALTIME 256 #define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME) #define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG) #define FUTEX_REQUEUE_PRIVATE (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG) #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_OP_PRIVATE (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG) #define FUTEX_LOCK_PI_PRIVATE (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG) #define FUTEX_WAIT_BITSET_PRIVATE (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG) #define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG) #define FUTEX_WAIT_REQUEUE_PI_PRIVATE (FUTEX_WAIT_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) #define FUTEX_CMP_REQUEUE_PI_PRIVATE (FUTEX_CMP_REQUEUE_PI | \ FUTEX_PRIVATE_FLAG) /* * Support for robust futexes: the kernel cleans up held futexes at * thread exit time. */ /* * Per-lock list entry - embedded in user-space locks, somewhere close * to the futex field. (Note: user-space uses a double-linked list to * achieve O(1) list add and remove, but the kernel only needs to know * about the forward link) * * NOTE: this structure is part of the syscall ABI, and must not be * changed. */ struct robust_list { struct robust_list *next; }; /* * Per-thread list head: * * NOTE: this structure is part of the syscall ABI, and must only be * changed if the change is first communicated with the glibc folks. * (When an incompatible change is done, we'll increase the structure * size, which glibc will detect) */ struct robust_list_head { /* * The head of the list. Points back to itself if empty: */ struct robust_list list; /* * This relative offset is set by user-space, it gives the kernel * the relative position of the futex field to examine. This way * we keep userspace flexible, to freely shape its data-structure, * without hardcoding any particular offset into the kernel: */ long futex_offset; /* * The death of the thread may race with userspace setting * up a lock's links. So to handle this race, userspace first * sets this field to the address of the to-be-taken lock, * then does the lock acquire, and then adds itself to the * list, and then clears this field. Hence the kernel will * always have full knowledge of all locks that the thread * _might_ have taken. We check the owner TID in any case, * so only truly owned locks will be handled. */ struct robust_list *list_op_pending; }; /* * Are there any waiters for this robust futex: */ #define FUTEX_WAITERS 0x80000000 /* * The kernel signals via this bit that a thread holding a futex * has exited without unlocking the futex. The kernel also does * a FUTEX_WAKE on such futexes, after setting the bit, to wake * up any possible waiters: */ #define FUTEX_OWNER_DIED 0x40000000 /* * The rest of the robust-futex field is for the TID: */ #define FUTEX_TID_MASK 0x3fffffff /* * This limit protects against a deliberately circular list. * (Not worth introducing an rlimit for it) */ #define ROBUST_LIST_LIMIT 2048 /* * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a * match of any bit. */ #define FUTEX_BITSET_MATCH_ANY 0xffffffff #define FUTEX_OP_SET 0 /* *(int *)UADDR2 = OPARG; */ #define FUTEX_OP_ADD 1 /* *(int *)UADDR2 += OPARG; */ #define FUTEX_OP_OR 2 /* *(int *)UADDR2 |= OPARG; */ #define FUTEX_OP_ANDN 3 /* *(int *)UADDR2 &= ~OPARG; */ #define FUTEX_OP_XOR 4 /* *(int *)UADDR2 ^= OPARG; */ #define FUTEX_OP_OPARG_SHIFT 8 /* Use (1 << OPARG) instead of OPARG. */ #define FUTEX_OP_CMP_EQ 0 /* if (oldval == CMPARG) wake */ #define FUTEX_OP_CMP_NE 1 /* if (oldval != CMPARG) wake */ #define FUTEX_OP_CMP_LT 2 /* if (oldval < CMPARG) wake */ #define FUTEX_OP_CMP_LE 3 /* if (oldval <= CMPARG) wake */ #define FUTEX_OP_CMP_GT 4 /* if (oldval > CMPARG) wake */ #define FUTEX_OP_CMP_GE 5 /* if (oldval >= CMPARG) wake */ /* FUTEX_WAKE_OP will perform atomically int oldval = *(int *)UADDR2; *(int *)UADDR2 = oldval OP OPARG; if (oldval CMP CMPARG) wake UADDR2; */ #define FUTEX_OP(op, oparg, cmp, cmparg) \ (((op & 0xf) << 28) | ((cmp & 0xf) << 24) \ | ((oparg & 0xfff) << 12) | (cmparg & 0xfff)) #endif /* _LINUX_FUTEX_H */
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