LXR linux/include/linux/futex.h

   1#ifndef _LINUX_FUTEX_H
   2#define _LINUX_FUTEX_H
   3
   4#include <linux/sched.h>
   5
   6/* Second argument to futex syscall */
   7
   8
   9#define FUTEX_WAIT              0
  10#define FUTEX_WAKE              1
  11#define FUTEX_FD                2
  12#define FUTEX_REQUEUE           3
  13#define FUTEX_CMP_REQUEUE       4
  14#define FUTEX_WAKE_OP           5
  15#define FUTEX_LOCK_PI           6
  16#define FUTEX_UNLOCK_PI         7
  17#define FUTEX_TRYLOCK_PI        8
  18
  19/*
  20 * Support for robust futexes: the kernel cleans up held futexes at
  21 * thread exit time.
  22 */
  23
  24/*
  25 * Per-lock list entry - embedded in user-space locks, somewhere close
  26 * to the futex field. (Note: user-space uses a double-linked list to
  27 * achieve O(1) list add and remove, but the kernel only needs to know
  28 * about the forward link)
  29 *
  30 * NOTE: this structure is part of the syscall ABI, and must not be
  31 * changed.
  32 */
  33struct robust_list {
  34        struct robust_list __user *next;
  35};
  36
  37/*
  38 * Per-thread list head:
  39 *
  40 * NOTE: this structure is part of the syscall ABI, and must only be
  41 * changed if the change is first communicated with the glibc folks.
  42 * (When an incompatible change is done, we'll increase the structure
  43 *  size, which glibc will detect)
  44 */
  45struct robust_list_head {
  46        /*
  47         * The head of the list. Points back to itself if empty:
  48         */
  49        struct robust_list list;
  50
  51        /*
  52         * This relative offset is set by user-space, it gives the kernel
  53         * the relative position of the futex field to examine. This way
  54         * we keep userspace flexible, to freely shape its data-structure,
  55         * without hardcoding any particular offset into the kernel:
  56         */
  57        long futex_offset;
  58
  59        /*
  60         * The death of the thread may race with userspace setting
  61         * up a lock's links. So to handle this race, userspace first
  62         * sets this field to the address of the to-be-taken lock,
  63         * then does the lock acquire, and then adds itself to the
  64         * list, and then clears this field. Hence the kernel will
  65         * always have full knowledge of all locks that the thread
  66         * _might_ have taken. We check the owner TID in any case,
  67         * so only truly owned locks will be handled.
  68         */
  69        struct robust_list __user *list_op_pending;
  70};
  71
  72/*
  73 * Are there any waiters for this robust futex:
  74 */
  75#define FUTEX_WAITERS           0x80000000
  76
  77/*
  78 * The kernel signals via this bit that a thread holding a futex
  79 * has exited without unlocking the futex. The kernel also does
  80 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  81 * up any possible waiters:
  82 */
  83#define FUTEX_OWNER_DIED        0x40000000
  84
  85/*
  86 * The rest of the robust-futex field is for the TID:
  87 */
  88#define FUTEX_TID_MASK          0x3fffffff
  89
  90/*
  91 * This limit protects against a deliberately circular list.
  92 * (Not worth introducing an rlimit for it)
  93 */
  94#define ROBUST_LIST_LIMIT       2048
  95
  96long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
  97              u32 __user *uaddr2, u32 val2, u32 val3);
  98
  99extern int
 100handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 101
 102#ifdef CONFIG_FUTEX
 103extern void exit_robust_list(struct task_struct *curr);
 104extern void exit_pi_state_list(struct task_struct *curr);
 105#else
 106static inline void exit_robust_list(struct task_struct *curr)
 107{
 108}
 109static inline void exit_pi_state_list(struct task_struct *curr)
 110{
 111}
 112#endif
 113
 114#define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 115#define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 116#define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 117#define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 118#define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 119
 120#define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 121
 122#define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 123#define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 124#define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 125#define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 126#define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 127#define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 128
 129/* FUTEX_WAKE_OP will perform atomically
 130   int oldval = *(int *)UADDR2;
 131   *(int *)UADDR2 = oldval OP OPARG;
 132   if (oldval CMP CMPARG)
 133     wake UADDR2;  */
 134
 135#define FUTEX_OP(op, oparg, cmp, cmparg) \
 136  (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 137   | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 138
 139#endif
 140