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linux-2.6/include/linux/futex.h
Thomas Gleixner cd689985cf futex: Add bitset conditional wait/wakeup functionality 
To allow the implementation of optimized rw-locks in user space, glibc
needs a possibility to select waiters for wakeup depending on a bitset
mask.

This requires two new futex OPs: FUTEX_WAIT_BITS and FUTEX_WAKE_BITS
These OPs are basically the same as FUTEX_WAIT and FUTEX_WAKE plus an
additional argument - a bitset. Further the FUTEX_WAIT_BITS OP is
expecting an absolute timeout value instead of the relative one, which
is used for the FUTEX_WAIT OP.

FUTEX_WAIT_BITS calls into the kernel with a bitset. The bitset is
stored in the futex_q structure, which is used to enqueue the waiter
into the hashed futex waitqueue.

FUTEX_WAKE_BITS also calls into the kernel with a bitset. The wakeup
function logically ANDs the bitset with the bitset stored in each
waiters futex_q structure. If the result is zero (i.e. none of the set
bits in the bitsets is matching), then the waiter is not woken up. If
the result is not zero (i.e. one of the set bits in the bitsets is
matching), then the waiter is woken.

The bitset provided by the caller must be non zero. In case the
provided bitset is zero the kernel returns EINVAL.

Internaly the new OPs are only extensions to the existing FUTEX_WAIT
and FUTEX_WAKE functions. The existing OPs hand a bitset with all bits
set into the futex_wait() and futex_wake() functions.

Signed-off-by: Thomas Gleixner <tgxl@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-02-01 17:45:14 +01:00

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#ifndef _LINUX_FUTEX_H
#define _LINUX_FUTEX_H
#include <linux/compiler.h>
#include <linux/types.h>
struct inode;
struct mm_struct;
struct task_struct;
union ktime;
/* 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_PRIVATE_FLAG 128
#define FUTEX_CMD_MASK ~FUTEX_PRIVATE_FLAG
#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_BITS | FUTEX_PRIVATE_FLAG)
#define FUTEX_WAKE_BITSET_PRIVATE (FUTEX_WAKE_BITS | 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 __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
#ifdef __KERNEL__
long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
u32 __user *uaddr2, u32 val2, u32 val3);
extern int
handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
/*
* Futexes are matched on equal values of this key.
* The key type depends on whether it's a shared or private mapping.
* Don't rearrange members without looking at hash_futex().
*
* offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
* We use the two low order bits of offset to tell what is the kind of key :
* 00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
* (no reference on an inode or mm)
* 01 : Shared futex (PTHREAD_PROCESS_SHARED)
* mapped on a file (reference on the underlying inode)
* 10 : Shared futex (PTHREAD_PROCESS_SHARED)
* (but private mapping on an mm, and reference taken on it)
*/
#define FUT_OFF_INODE 1 /* We set bit 0 if key has a reference on inode */
#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
union futex_key {
struct {
unsigned long pgoff;
struct inode *inode;
int offset;
} shared;
struct {
unsigned long address;
struct mm_struct *mm;
int offset;
} private;
struct {
unsigned long word;
void *ptr;
int offset;
} both;
};
#ifdef CONFIG_FUTEX
extern void exit_robust_list(struct task_struct *curr);
extern void exit_pi_state_list(struct task_struct *curr);
#else
static inline void exit_robust_list(struct task_struct *curr)
{
}
static inline void exit_pi_state_list(struct task_struct *curr)
{
}
#endif
#endif /* __KERNEL__ */
#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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