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