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futex.h
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futex.h
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/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
#ifndef _UAPI_LINUX_FUTEX_H
#define _UAPI_LINUX_FUTEX_H
#include <linux/compiler.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_LOCK_PI2 13
#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_LOCK_PI2_PRIVATE (FUTEX_LOCK_PI2 | 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)
#define FUTEX_32 2
#define FUTEX_SHARED_FLAG 8
#define FUTEX_SIZE_MASK 0x3
/*
* 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 __user *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 __user *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 /* _UAPI_LINUX_FUTEX_H */