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#ifndef _LINUX_FUTEX_H
#define _LINUX_FUTEX_H
#include <linux/sched.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
/*
* 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
/*
* Reserved bit:
*/
#define FUTEX_OWNER_PENDING 0x20000000
/*
* The rest of the robust-futex field is for the TID:
*/
#define FUTEX_TID_MASK 0x1fffffff
/*
* A limit of one million locks held per thread (!) ought to be enough
* for some time. This also protects against a deliberately circular
* list. Not worth introducing an rlimit for this:
*/
#define ROBUST_LIST_LIMIT 1048576
long do_futex(unsigned long uaddr, int op, int val,
unsigned long timeout, unsigned long uaddr2, int val2,
int val3);
extern int handle_futex_death(unsigned int *uaddr, struct task_struct *curr);
#ifdef CONFIG_FUTEX
extern void exit_robust_list(struct task_struct *curr);
#else
static inline void exit_robust_list(struct task_struct *curr)
{
}
#endif
#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
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