include/linux/futex.h

   1 #ifndef _LINUX_FUTEX_H
   2 #define _LINUX_FUTEX_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/types.h>
   6
   7 struct inode;
   8 struct mm_struct;
   9 struct task_struct;
  10 union ktime;
  11
  12 /* Second argument to futex syscall */
  13
  14
  15 #define FUTEX_WAIT              0
  16 #define FUTEX_WAKE              1
  17 #define FUTEX_FD                2
  18 #define FUTEX_REQUEUE           3
  19 #define FUTEX_CMP_REQUEUE       4
  20 #define FUTEX_WAKE_OP           5
  21 #define FUTEX_LOCK_PI           6
  22 #define FUTEX_UNLOCK_PI         7
  23 #define FUTEX_TRYLOCK_PI        8
  24 #define FUTEX_WAIT_BITSET       9
  25 #define FUTEX_WAKE_BITSET       10
  26 #define FUTEX_WAIT_REQUEUE_PI   11
  27 #define FUTEX_CMP_REQUEUE_PI    12
  28
  29 #define FUTEX_PRIVATE_FLAG      128
  30 #define FUTEX_CLOCK_REALTIME    256
  31 #define FUTEX_CMD_MASK          ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
  32
  33 #define FUTEX_WAIT_PRIVATE      (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
  34 #define FUTEX_WAKE_PRIVATE      (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
  35 #define FUTEX_REQUEUE_PRIVATE   (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
  36 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
  37 #define FUTEX_WAKE_OP_PRIVATE   (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
  38 #define FUTEX_LOCK_PI_PRIVATE   (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
  39 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
  40 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
  41 #define FUTEX_WAIT_BITSET_PRIVATE       (FUTEX_WAIT_BITS | FUTEX_PRIVATE_FLAG)
  42 #define FUTEX_WAKE_BITSET_PRIVATE       (FUTEX_WAKE_BITS | FUTEX_PRIVATE_FLAG)
  43 #define FUTEX_WAIT_REQUEUE_PI_PRIVATE   (FUTEX_WAIT_REQUEUE_PI | \
  44                                          FUTEX_PRIVATE_FLAG)
  45 #define FUTEX_CMP_REQUEUE_PI_PRIVATE    (FUTEX_CMP_REQUEUE_PI | \
  46                                          FUTEX_PRIVATE_FLAG)
  47
  48 /*
  49  * Support for robust futexes: the kernel cleans up held futexes at
  50  * thread exit time.
  51  */
  52
  53 /*
  54  * Per-lock list entry - embedded in user-space locks, somewhere close
  55  * to the futex field. (Note: user-space uses a double-linked list to
  56  * achieve O(1) list add and remove, but the kernel only needs to know
  57  * about the forward link)
  58  *
  59  * NOTE: this structure is part of the syscall ABI, and must not be
  60  * changed.
  61  */
  62 struct robust_list {
  63         struct robust_list __user *next;
  64 };
  65
  66 /*
  67  * Per-thread list head:
  68  *
  69  * NOTE: this structure is part of the syscall ABI, and must only be
  70  * changed if the change is first communicated with the glibc folks.
  71  * (When an incompatible change is done, we'll increase the structure
  72  *  size, which glibc will detect)
  73  */
  74 struct robust_list_head {
  75         /*
  76          * The head of the list. Points back to itself if empty:
  77          */
  78         struct robust_list list;
  79
  80         /*
  81          * This relative offset is set by user-space, it gives the kernel
  82          * the relative position of the futex field to examine. This way
  83          * we keep userspace flexible, to freely shape its data-structure,
  84          * without hardcoding any particular offset into the kernel:
  85          */
  86         long futex_offset;
  87
  88         /*
  89          * The death of the thread may race with userspace setting
  90          * up a lock's links. So to handle this race, userspace first
  91          * sets this field to the address of the to-be-taken lock,
  92          * then does the lock acquire, and then adds itself to the
  93          * list, and then clears this field. Hence the kernel will
  94          * always have full knowledge of all locks that the thread
  95          * _might_ have taken. We check the owner TID in any case,
  96          * so only truly owned locks will be handled.
  97          */
  98         struct robust_list __user *list_op_pending;
  99 };
 100
 101 /*
 102  * Are there any waiters for this robust futex:
 103  */
 104 #define FUTEX_WAITERS           0x80000000
 105
 106 /*
 107  * The kernel signals via this bit that a thread holding a futex
 108  * has exited without unlocking the futex. The kernel also does
 109  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
 110  * up any possible waiters:
 111  */
 112 #define FUTEX_OWNER_DIED        0x40000000
 113
 114 /*
 115  * The rest of the robust-futex field is for the TID:
 116  */
 117 #define FUTEX_TID_MASK          0x3fffffff
 118
 119 /*
 120  * This limit protects against a deliberately circular list.
 121  * (Not worth introducing an rlimit for it)
 122  */
 123 #define ROBUST_LIST_LIMIT       2048
 124
 125 /*
 126  * bitset with all bits set for the FUTEX_xxx_BITSET OPs to request a
 127  * match of any bit.
 128  */
 129 #define FUTEX_BITSET_MATCH_ANY  0xffffffff
 130
 131 #ifdef __KERNEL__
 132 long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
 133               u32 __user *uaddr2, u32 val2, u32 val3);
 134
 135 extern int
 136 handle_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
 156 union 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
 177 extern void exit_robust_list(struct task_struct *curr);
 178 extern void exit_pi_state_list(struct task_struct *curr);
 179 extern int futex_cmpxchg_enabled;
 180 #else
 181 static inline void exit_robust_list(struct task_struct *curr)
 182 {
 183 }
 184 static 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