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 /*
  22  * Support for robust futexes: the kernel cleans up held futexes at
  23  * thread exit time.
  24  */
  25
  26 /*
  27  * Per-lock list entry - embedded in user-space locks, somewhere close
  28  * to the futex field. (Note: user-space uses a double-linked list to
  29  * achieve O(1) list add and remove, but the kernel only needs to know
  30  * about the forward link)
  31  *
  32  * NOTE: this structure is part of the syscall ABI, and must not be
  33  * changed.
  34  */
  35 struct robust_list {
  36         struct robust_list __user *next;
  37 };
  38
  39 /*
  40  * Per-thread list head:
  41  *
  42  * NOTE: this structure is part of the syscall ABI, and must only be
  43  * changed if the change is first communicated with the glibc folks.
  44  * (When an incompatible change is done, we'll increase the structure
  45  *  size, which glibc will detect)
  46  */
  47 struct robust_list_head {
  48         /*
  49          * The head of the list. Points back to itself if empty:
  50          */
  51         struct robust_list list;
  52
  53         /*
  54          * This relative offset is set by user-space, it gives the kernel
  55          * the relative position of the futex field to examine. This way
  56          * we keep userspace flexible, to freely shape its data-structure,
  57          * without hardcoding any particular offset into the kernel:
  58          */
  59         long futex_offset;
  60
  61         /*
  62          * The death of the thread may race with userspace setting
  63          * up a lock's links. So to handle this race, userspace first
  64          * sets this field to the address of the to-be-taken lock,
  65          * then does the lock acquire, and then adds itself to the
  66          * list, and then clears this field. Hence the kernel will
  67          * always have full knowledge of all locks that the thread
  68          * _might_ have taken. We check the owner TID in any case,
  69          * so only truly owned locks will be handled.
  70          */
  71         struct robust_list __user *list_op_pending;
  72 };
  73
  74 /*
  75  * Are there any waiters for this robust futex:
  76  */
  77 #define FUTEX_WAITERS           0x80000000
  78
  79 /*
  80  * The kernel signals via this bit that a thread holding a futex
  81  * has exited without unlocking the futex. The kernel also does
  82  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  83  * up any possible waiters:
  84  */
  85 #define FUTEX_OWNER_DIED        0x40000000
  86
  87 /*
  88  * The rest of the robust-futex field is for the TID:
  89  */
  90 #define FUTEX_TID_MASK          0x3fffffff
  91
  92 /*
  93  * This limit protects against a deliberately circular list.
  94  * (Not worth introducing an rlimit for it)
  95  */
  96 #define ROBUST_LIST_LIMIT       2048
  97
  98 #ifdef __KERNEL__
  99 long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
 100               u32 __user *uaddr2, u32 val2, u32 val3);
 101
 102 extern int
 103 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 104
 105 /*
 106  * Futexes are matched on equal values of this key.
 107  * The key type depends on whether it's a shared or private mapping.
 108  * Don't rearrange members without looking at hash_futex().
 109  *
 110  * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
 111  * We set bit 0 to indicate if it's an inode-based key.
 112  */
 113 union futex_key {
 114         struct {
 115                 unsigned long pgoff;
 116                 struct inode *inode;
 117                 int offset;
 118         } shared;
 119         struct {
 120                 unsigned long address;
 121                 struct mm_struct *mm;
 122                 int offset;
 123         } private;
 124         struct {
 125                 unsigned long word;
 126                 void *ptr;
 127                 int offset;
 128         } both;
 129 };
 130 int get_futex_key(u32 __user *uaddr, union futex_key *key);
 131 void get_futex_key_refs(union futex_key *key);
 132 void drop_futex_key_refs(union futex_key *key);
 133
 134 #ifdef CONFIG_FUTEX
 135 extern void exit_robust_list(struct task_struct *curr);
 136 extern void exit_pi_state_list(struct task_struct *curr);
 137 #else
 138 static inline void exit_robust_list(struct task_struct *curr)
 139 {
 140 }
 141 static inline void exit_pi_state_list(struct task_struct *curr)
 142 {
 143 }
 144 #endif
 145 #endif /* __KERNEL__ */
 146
 147 #define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 148 #define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 149 #define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 150 #define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 151 #define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 152
 153 #define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 154
 155 #define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 156 #define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 157 #define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 158 #define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 159 #define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 160 #define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 161
 162 /* FUTEX_WAKE_OP will perform atomically
 163    int oldval = *(int *)UADDR2;
 164    *(int *)UADDR2 = oldval OP OPARG;
 165    if (oldval CMP CMPARG)
 166      wake UADDR2;  */
 167
 168 #define FUTEX_OP(op, oparg, cmp, cmparg) \
 169   (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 170    | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 171
 172 #endif