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