include/linux/futex.h

   1 #ifndef _LINUX_FUTEX_H
   2 #define _LINUX_FUTEX_H
   3
   4 #include <linux/sched.h>
   5
   6 /* Second argument to futex syscall */
   7
   8
   9 #define FUTEX_WAIT              0
  10 #define FUTEX_WAKE              1
  11 #define FUTEX_FD                2
  12 #define FUTEX_REQUEUE           3
  13 #define FUTEX_CMP_REQUEUE       4
  14 #define FUTEX_WAKE_OP           5
  15
  16 /*
  17  * Support for robust futexes: the kernel cleans up held futexes at
  18  * thread exit time.
  19  */
  20
  21 /*
  22  * Per-lock list entry - embedded in user-space locks, somewhere close
  23  * to the futex field. (Note: user-space uses a double-linked list to
  24  * achieve O(1) list add and remove, but the kernel only needs to know
  25  * about the forward link)
  26  *
  27  * NOTE: this structure is part of the syscall ABI, and must not be
  28  * changed.
  29  */
  30 struct robust_list {
  31         struct robust_list __user *next;
  32 };
  33
  34 /*
  35  * Per-thread list head:
  36  *
  37  * NOTE: this structure is part of the syscall ABI, and must only be
  38  * changed if the change is first communicated with the glibc folks.
  39  * (When an incompatible change is done, we'll increase the structure
  40  *  size, which glibc will detect)
  41  */
  42 struct robust_list_head {
  43         /*
  44          * The head of the list. Points back to itself if empty:
  45          */
  46         struct robust_list list;
  47
  48         /*
  49          * This relative offset is set by user-space, it gives the kernel
  50          * the relative position of the futex field to examine. This way
  51          * we keep userspace flexible, to freely shape its data-structure,
  52          * without hardcoding any particular offset into the kernel:
  53          */
  54         long futex_offset;
  55
  56         /*
  57          * The death of the thread may race with userspace setting
  58          * up a lock's links. So to handle this race, userspace first
  59          * sets this field to the address of the to-be-taken lock,
  60          * then does the lock acquire, and then adds itself to the
  61          * list, and then clears this field. Hence the kernel will
  62          * always have full knowledge of all locks that the thread
  63          * _might_ have taken. We check the owner TID in any case,
  64          * so only truly owned locks will be handled.
  65          */
  66         struct robust_list __user *list_op_pending;
  67 };
  68
  69 /*
  70  * Are there any waiters for this robust futex:
  71  */
  72 #define FUTEX_WAITERS           0x80000000
  73
  74 /*
  75  * The kernel signals via this bit that a thread holding a futex
  76  * has exited without unlocking the futex. The kernel also does
  77  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  78  * up any possible waiters:
  79  */
  80 #define FUTEX_OWNER_DIED        0x40000000
  81
  82 /*
  83  * The rest of the robust-futex field is for the TID:
  84  */
  85 #define FUTEX_TID_MASK          0x3fffffff
  86
  87 /*
  88  * This limit protects against a deliberately circular list.
  89  * (Not worth introducing an rlimit for it)
  90  */
  91 #define ROBUST_LIST_LIMIT       2048
  92
  93 long do_futex(unsigned long uaddr, int op, int val,
  94                 unsigned long timeout, unsigned long uaddr2, int val2,
  95                 int val3);
  96
  97 extern int handle_futex_death(u32 __user *uaddr, struct task_struct *curr);
  98
  99 #ifdef CONFIG_FUTEX
 100 extern void exit_robust_list(struct task_struct *curr);
 101 #else
 102 static inline void exit_robust_list(struct task_struct *curr)
 103 {
 104 }
 105 #endif
 106
 107 #define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 108 #define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 109 #define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 110 #define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 111 #define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 112
 113 #define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 114
 115 #define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 116 #define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 117 #define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 118 #define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 119 #define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 120 #define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 121
 122 /* FUTEX_WAKE_OP will perform atomically
 123    int oldval = *(int *)UADDR2;
 124    *(int *)UADDR2 = oldval OP OPARG;
 125    if (oldval CMP CMPARG)
 126      wake UADDR2;  */
 127
 128 #define FUTEX_OP(op, oparg, cmp, cmparg) \
 129   (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 130    | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 131
 132 #endif