include/linux/futex.h

   1 #ifndef _LINUX_FUTEX_H
   2 #define _LINUX_FUTEX_H
   3
   4 #include <linux/sched.h>
   5
   6 union ktime;
   7
   8 /* Second argument to futex syscall */
   9
  10
  11 #define FUTEX_WAIT              0
  12 #define FUTEX_WAKE              1
  13 #define FUTEX_FD                2
  14 #define FUTEX_REQUEUE           3
  15 #define FUTEX_CMP_REQUEUE       4
  16 #define FUTEX_WAKE_OP           5
  17 #define FUTEX_LOCK_PI           6
  18 #define FUTEX_UNLOCK_PI         7
  19 #define FUTEX_TRYLOCK_PI        8
  20 #define FUTEX_CMP_REQUEUE_PI    9
  21
  22 #define FUTEX_PRIVATE_FLAG      128
  23 #define FUTEX_CMD_MASK          ~FUTEX_PRIVATE_FLAG
  24
  25 #define FUTEX_WAIT_PRIVATE      (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
  26 #define FUTEX_WAKE_PRIVATE      (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
  27 #define FUTEX_REQUEUE_PRIVATE   (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
  28 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
  29 #define FUTEX_WAKE_OP_PRIVATE   (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
  30 #define FUTEX_LOCK_PI_PRIVATE   (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
  31 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
  32 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
  33
  34 /*
  35  * Support for robust futexes: the kernel cleans up held futexes at
  36  * thread exit time.
  37  */
  38
  39 /*
  40  * Per-lock list entry - embedded in user-space locks, somewhere close
  41  * to the futex field. (Note: user-space uses a double-linked list to
  42  * achieve O(1) list add and remove, but the kernel only needs to know
  43  * about the forward link)
  44  *
  45  * NOTE: this structure is part of the syscall ABI, and must not be
  46  * changed.
  47  */
  48 struct robust_list {
  49         struct robust_list __user *next;
  50 };
  51
  52 /*
  53  * Per-thread list head:
  54  *
  55  * NOTE: this structure is part of the syscall ABI, and must only be
  56  * changed if the change is first communicated with the glibc folks.
  57  * (When an incompatible change is done, we'll increase the structure
  58  *  size, which glibc will detect)
  59  */
  60 struct robust_list_head {
  61         /*
  62          * The head of the list. Points back to itself if empty:
  63          */
  64         struct robust_list list;
  65
  66         /*
  67          * This relative offset is set by user-space, it gives the kernel
  68          * the relative position of the futex field to examine. This way
  69          * we keep userspace flexible, to freely shape its data-structure,
  70          * without hardcoding any particular offset into the kernel:
  71          */
  72         long futex_offset;
  73
  74         /*
  75          * The death of the thread may race with userspace setting
  76          * up a lock's links. So to handle this race, userspace first
  77          * sets this field to the address of the to-be-taken lock,
  78          * then does the lock acquire, and then adds itself to the
  79          * list, and then clears this field. Hence the kernel will
  80          * always have full knowledge of all locks that the thread
  81          * _might_ have taken. We check the owner TID in any case,
  82          * so only truly owned locks will be handled.
  83          */
  84         struct robust_list __user *list_op_pending;
  85 };
  86
  87 /*
  88  * Are there any waiters for this robust futex:
  89  */
  90 #define FUTEX_WAITERS           0x80000000
  91
  92 /*
  93  * The kernel signals via this bit that a thread holding a futex
  94  * has exited without unlocking the futex. The kernel also does
  95  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  96  * up any possible waiters:
  97  */
  98 #define FUTEX_OWNER_DIED        0x40000000
  99
 100 /*
 101  * Some processes have been requeued on this PI-futex
 102  */
 103 #define FUTEX_WAITER_REQUEUED   0x20000000
 104
 105 /*
 106  * The rest of the robust-futex field is for the TID:
 107  */
 108 #define FUTEX_TID_MASK          0x0fffffff
 109
 110 /*
 111  * This limit protects against a deliberately circular list.
 112  * (Not worth introducing an rlimit for it)
 113  */
 114 #define ROBUST_LIST_LIMIT       2048
 115
 116 #ifdef __KERNEL__
 117 long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
 118               u32 __user *uaddr2, u32 val2, u32 val3);
 119
 120 extern int
 121 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 122
 123 /*
 124  * Futexes are matched on equal values of this key.
 125  * The key type depends on whether it's a shared or private mapping.
 126  * Don't rearrange members without looking at hash_futex().
 127  *
 128  * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
 129  * We use the two low order bits of offset to tell what is the kind of key :
 130  *  00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
 131  *       (no reference on an inode or mm)
 132  *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
 133  *      mapped on a file (reference on the underlying inode)
 134  *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
 135  *       (but private mapping on an mm, and reference taken on it)
 136 */
 137
 138 #define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
 139 #define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
 140
 141 union futex_key {
 142         u32 __user *uaddr;
 143         struct {
 144                 unsigned long pgoff;
 145                 struct inode *inode;
 146                 int offset;
 147         } shared;
 148         struct {
 149                 unsigned long address;
 150                 struct mm_struct *mm;
 151                 int offset;
 152         } private;
 153         struct {
 154                 unsigned long word;
 155                 void *ptr;
 156                 int offset;
 157         } both;
 158 };
 159 int get_futex_key(u32 __user *uaddr, struct rw_semaphore *shared,
 160                   union futex_key *key);
 161 void get_futex_key_refs(union futex_key *key);
 162 void drop_futex_key_refs(union futex_key *key);
 163
 164 #ifdef CONFIG_FUTEX
 165 extern void exit_robust_list(struct task_struct *curr);
 166 extern void exit_pi_state_list(struct task_struct *curr);
 167 #else
 168 static inline void exit_robust_list(struct task_struct *curr)
 169 {
 170 }
 171 static inline void exit_pi_state_list(struct task_struct *curr)
 172 {
 173 }
 174 #endif
 175 #endif /* __KERNEL__ */
 176
 177 #define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 178 #define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 179 #define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 180 #define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 181 #define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 182
 183 #define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 184
 185 #define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 186 #define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 187 #define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 188 #define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 189 #define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 190 #define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 191
 192 /* FUTEX_WAKE_OP will perform atomically
 193    int oldval = *(int *)UADDR2;
 194    *(int *)UADDR2 = oldval OP OPARG;
 195    if (oldval CMP CMPARG)
 196      wake UADDR2;  */
 197
 198 #define FUTEX_OP(op, oparg, cmp, cmparg) \
 199   (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 200    | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 201
 202 #endif