linux/include/linux/futex.h
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   1#ifndef _LINUX_FUTEX_H
   2#define _LINUX_FUTEX_H
   3
   4#include <linux/compiler.h>
   5#include <linux/types.h>
   6
   7/* Second argument to futex syscall */
   8
   9
  10#define FUTEX_WAIT              0
  11#define FUTEX_WAKE              1
  12#define FUTEX_FD                2
  13#define FUTEX_REQUEUE           3
  14#define FUTEX_CMP_REQUEUE       4
  15#define FUTEX_WAKE_OP           5
  16#define FUTEX_LOCK_PI           6
  17#define FUTEX_UNLOCK_PI         7
  18#define FUTEX_TRYLOCK_PI        8
  19#define FUTEX_WAIT_BITSET       9
  20#define FUTEX_WAKE_BITSET       10
  21#define FUTEX_WAIT_REQUEUE_PI   11
  22#define FUTEX_CMP_REQUEUE_PI    12
  23
  24#define FUTEX_PRIVATE_FLAG      128
  25#define FUTEX_CLOCK_REALTIME    256
  26#define FUTEX_CMD_MASK          ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
  27
  28#define FUTEX_WAIT_PRIVATE      (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
  29#define FUTEX_WAKE_PRIVATE      (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
  30#define FUTEX_REQUEUE_PRIVATE   (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
  31#define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
  32#define FUTEX_WAKE_OP_PRIVATE   (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
  33#define FUTEX_LOCK_PI_PRIVATE   (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
  34#define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
  35#define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
  36#define FUTEX_WAIT_BITSET_PRIVATE       (FUTEX_WAIT_BITSET | FUTEX_PRIVATE_FLAG)
  37#define FUTEX_WAKE_BITSET_PRIVATE       (FUTEX_WAKE_BITSET | FUTEX_PRIVATE_FLAG)
  38#define FUTEX_WAIT_REQUEUE_PI_PRIVATE   (FUTEX_WAIT_REQUEUE_PI | \
  39                                         FUTEX_PRIVATE_FLAG)
  40#define FUTEX_CMP_REQUEUE_PI_PRIVATE    (FUTEX_CMP_REQUEUE_PI | \
  41                                         FUTEX_PRIVATE_FLAG)
  42
  43/*
  44 * Support for robust futexes: the kernel cleans up held futexes at
  45 * thread exit time.
  46 */
  47
  48/*
  49 * Per-lock list entry - embedded in user-space locks, somewhere close
  50 * to the futex field. (Note: user-space uses a double-linked list to
  51 * achieve O(1) list add and remove, but the kernel only needs to know
  52 * about the forward link)
  53 *
  54 * NOTE: this structure is part of the syscall ABI, and must not be
  55 * changed.
  56 */
  57struct robust_list {
  58        struct robust_list __user *next;
  59};
  60
  61/*
  62 * Per-thread list head:
  63 *
  64 * NOTE: this structure is part of the syscall ABI, and must only be
  65 * changed if the change is first communicated with the glibc folks.
  66 * (When an incompatible change is done, we'll increase the structure
  67 *  size, which glibc will detect)
  68 */
  69struct robust_list_head {
  70        /*
  71         * The head of the list. Points back to itself if empty:
  72         */
  73        struct robust_list list;
  74
  75        /*
  76         * This relative offset is set by user-space, it gives the kernel
  77         * the relative position of the futex field to examine. This way
  78         * we keep userspace flexible, to freely shape its data-structure,
  79         * without hardcoding any particular offset into the kernel:
  80         */
  81        long futex_offset;
  82
  83        /*
  84         * The death of the thread may race with userspace setting
  85         * up a lock's links. So to handle this race, userspace first
  86         * sets this field to the address of the to-be-taken lock,
  87         * then does the lock acquire, and then adds itself to the
  88         * list, and then clears this field. Hence the kernel will
  89         * always have full knowledge of all locks that the thread
  90         * _might_ have taken. We check the owner TID in any case,
  91         * so only truly owned locks will be handled.
  92         */
  93        struct robust_list __user *list_op_pending;
  94};
  95
  96/*
  97 * Are there any waiters for this robust futex:
  98 */
  99#define FUTEX_WAITERS           0x80000000
 100
 101/*
 102 * The kernel signals via this bit that a thread holding a futex
 103 * has exited without unlocking the futex. The kernel also does
 104 * a FUTEX_WAKE on such futexes, after setting the bit, to wake
 105 * up any possible waiters:
 106 */
 107#define FUTEX_OWNER_DIED        0x40000000
 108
 109/*
 110 * The rest of the robust-futex field is for the TID:
 111 */
 112#define FUTEX_TID_MASK          0x3fffffff
 113
 114/*
 115 * This limit protects against a deliberately circular list.
 116 * (Not worth introducing an rlimit for it)
 117 */
 118#define ROBUST_LIST_LIMIT       2048
 119
 120/*
 121 * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
 122 * match of any bit.
 123 */
 124#define FUTEX_BITSET_MATCH_ANY  0xffffffff
 125
 126#ifdef __KERNEL__
 127struct inode;
 128struct mm_struct;
 129struct task_struct;
 130union ktime;
 131
 132long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
 133              u32 __user *uaddr2, u32 val2, u32 val3);
 134
 135extern int
 136handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 137
 138/*
 139 * Futexes are matched on equal values of this key.
 140 * The key type depends on whether it's a shared or private mapping.
 141 * Don't rearrange members without looking at hash_futex().
 142 *
 143 * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
 144 * We use the two low order bits of offset to tell what is the kind of key :
 145 *  00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
 146 *       (no reference on an inode or mm)
 147 *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
 148 *      mapped on a file (reference on the underlying inode)
 149 *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
 150 *       (but private mapping on an mm, and reference taken on it)
 151*/
 152
 153#define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
 154#define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
 155
 156union futex_key {
 157        struct {
 158                unsigned long pgoff;
 159                struct inode *inode;
 160                int offset;
 161        } shared;
 162        struct {
 163                unsigned long address;
 164                struct mm_struct *mm;
 165                int offset;
 166        } private;
 167        struct {
 168                unsigned long word;
 169                void *ptr;
 170                int offset;
 171        } both;
 172};
 173
 174#define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
 175
 176#ifdef CONFIG_FUTEX
 177extern void exit_robust_list(struct task_struct *curr);
 178extern void exit_pi_state_list(struct task_struct *curr);
 179extern int futex_cmpxchg_enabled;
 180#else
 181static inline void exit_robust_list(struct task_struct *curr)
 182{
 183}
 184static inline void exit_pi_state_list(struct task_struct *curr)
 185{
 186}
 187#endif
 188#endif /* __KERNEL__ */
 189
 190#define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 191#define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 192#define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 193#define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 194#define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 195
 196#define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 197
 198#define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 199#define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 200#define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 201#define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 202#define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 203#define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 204
 205/* FUTEX_WAKE_OP will perform atomically
 206   int oldval = *(int *)UADDR2;
 207   *(int *)UADDR2 = oldval OP OPARG;
 208   if (oldval CMP CMPARG)
 209     wake UADDR2;  */
 210
 211#define FUTEX_OP(op, oparg, cmp, cmparg) \
 212  (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 213   | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 214
 215#endif
 216
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