futex.h

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#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_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 __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 */