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