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 #define FUTEX_LOCK_PI           6
  16 #define FUTEX_UNLOCK_PI         7
  17 #define FUTEX_TRYLOCK_PI        8
  18
  19 /*
  20  * Support for robust futexes: the kernel cleans up held futexes at
  21  * thread exit time.
  22  */
  23
  24 /*
  25  * Per-lock list entry - embedded in user-space locks, somewhere close
  26  * to the futex field. (Note: user-space uses a double-linked list to
  27  * achieve O(1) list add and remove, but the kernel only needs to know
  28  * about the forward link)
  29  *
  30  * NOTE: this structure is part of the syscall ABI, and must not be
  31  * changed.
  32  */
  33 struct robust_list {
  34         struct robust_list __user *next;
  35 };
  36
  37 /*
  38  * Per-thread list head:
  39  *
  40  * NOTE: this structure is part of the syscall ABI, and must only be
  41  * changed if the change is first communicated with the glibc folks.
  42  * (When an incompatible change is done, we'll increase the structure
  43  *  size, which glibc will detect)
  44  */
  45 struct robust_list_head {
  46         /*
  47          * The head of the list. Points back to itself if empty:
  48          */
  49         struct robust_list list;
  50
  51         /*
  52          * This relative offset is set by user-space, it gives the kernel
  53          * the relative position of the futex field to examine. This way
  54          * we keep userspace flexible, to freely shape its data-structure,
  55          * without hardcoding any particular offset into the kernel:
  56          */
  57         long futex_offset;
  58
  59         /*
  60          * The death of the thread may race with userspace setting
  61          * up a lock's links. So to handle this race, userspace first
  62          * sets this field to the address of the to-be-taken lock,
  63          * then does the lock acquire, and then adds itself to the
  64          * list, and then clears this field. Hence the kernel will
  65          * always have full knowledge of all locks that the thread
  66          * _might_ have taken. We check the owner TID in any case,
  67          * so only truly owned locks will be handled.
  68          */
  69         struct robust_list __user *list_op_pending;
  70 };
  71
  72 /*
  73  * Are there any waiters for this robust futex:
  74  */
  75 #define FUTEX_WAITERS           0x80000000
  76
  77 /*
  78  * The kernel signals via this bit that a thread holding a futex
  79  * has exited without unlocking the futex. The kernel also does
  80  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  81  * up any possible waiters:
  82  */
  83 #define FUTEX_OWNER_DIED        0x40000000
  84
  85 /*
  86  * The rest of the robust-futex field is for the TID:
  87  */
  88 #define FUTEX_TID_MASK          0x3fffffff
  89
  90 /*
  91  * This limit protects against a deliberately circular list.
  92  * (Not worth introducing an rlimit for it)
  93  */
  94 #define ROBUST_LIST_LIMIT       2048
  95
  96 long do_futex(u32 __user *uaddr, int op, u32 val, unsigned long timeout,
  97               u32 __user *uaddr2, u32 val2, u32 val3);
  98
  99 extern int
 100 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 101
 102 #ifdef CONFIG_FUTEX
 103 extern void exit_robust_list(struct task_struct *curr);
 104 extern void exit_pi_state_list(struct task_struct *curr);
 105 #else
 106 static inline void exit_robust_list(struct task_struct *curr)
 107 {
 108 }
 109 static inline void exit_pi_state_list(struct task_struct *curr)
 110 {
 111 }
 112 #endif
 113
 114 #define FUTEX_OP_SET            0       /* *(int *)UADDR2 = OPARG; */
 115 #define FUTEX_OP_ADD            1       /* *(int *)UADDR2 += OPARG; */
 116 #define FUTEX_OP_OR             2       /* *(int *)UADDR2 |= OPARG; */
 117 #define FUTEX_OP_ANDN           3       /* *(int *)UADDR2 &= ~OPARG; */
 118 #define FUTEX_OP_XOR            4       /* *(int *)UADDR2 ^= OPARG; */
 119
 120 #define FUTEX_OP_OPARG_SHIFT    8       /* Use (1 << OPARG) instead of OPARG.  */
 121
 122 #define FUTEX_OP_CMP_EQ         0       /* if (oldval == CMPARG) wake */
 123 #define FUTEX_OP_CMP_NE         1       /* if (oldval != CMPARG) wake */
 124 #define FUTEX_OP_CMP_LT         2       /* if (oldval < CMPARG) wake */
 125 #define FUTEX_OP_CMP_LE         3       /* if (oldval <= CMPARG) wake */
 126 #define FUTEX_OP_CMP_GT         4       /* if (oldval > CMPARG) wake */
 127 #define FUTEX_OP_CMP_GE         5       /* if (oldval >= CMPARG) wake */
 128
 129 /* FUTEX_WAKE_OP will perform atomically
 130    int oldval = *(int *)UADDR2;
 131    *(int *)UADDR2 = oldval OP OPARG;
 132    if (oldval CMP CMPARG)
 133      wake UADDR2;  */
 134
 135 #define FUTEX_OP(op, oparg, cmp, cmparg) \
 136   (((op & 0xf) << 28) | ((cmp & 0xf) << 24)             \
 137    | ((oparg & 0xfff) << 12) | (cmparg & 0xfff))
 138
 139 #endif