include/linux/futex.h

   1 #ifndef _LINUX_FUTEX_H
   2 #define _LINUX_FUTEX_H
   3
   4 #include <linux/compiler.h>
   5 #include <linux/types.h>
   6
   7 struct inode;
   8 struct mm_struct;
   9 struct task_struct;
  10 union ktime;
  11
  12 /* Second argument to futex syscall */
  13
  14
  15 #define FUTEX_WAIT              0
  16 #define FUTEX_WAKE              1
  17 #define FUTEX_FD                2
  18 #define FUTEX_REQUEUE           3
  19 #define FUTEX_CMP_REQUEUE       4
  20 #define FUTEX_WAKE_OP           5
  21 #define FUTEX_LOCK_PI           6
  22 #define FUTEX_UNLOCK_PI         7
  23 #define FUTEX_TRYLOCK_PI        8
  24
  25 #define FUTEX_PRIVATE_FLAG      128
  26 #define FUTEX_CMD_MASK          ~FUTEX_PRIVATE_FLAG
  27
  28 #define FUTEX_WAIT_PRIVATE      (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
  29 #define FUTEX_WAKE_PRIVATE      (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
  30 #define FUTEX_REQUEUE_PRIVATE   (FUTEX_REQUEUE | FUTEX_PRIVATE_FLAG)
  31 #define FUTEX_CMP_REQUEUE_PRIVATE (FUTEX_CMP_REQUEUE | FUTEX_PRIVATE_FLAG)
  32 #define FUTEX_WAKE_OP_PRIVATE   (FUTEX_WAKE_OP | FUTEX_PRIVATE_FLAG)
  33 #define FUTEX_LOCK_PI_PRIVATE   (FUTEX_LOCK_PI | FUTEX_PRIVATE_FLAG)
  34 #define FUTEX_UNLOCK_PI_PRIVATE (FUTEX_UNLOCK_PI | FUTEX_PRIVATE_FLAG)
  35 #define FUTEX_TRYLOCK_PI_PRIVATE (FUTEX_TRYLOCK_PI | FUTEX_PRIVATE_FLAG)
  36
  37 /*
  38  * Support for robust futexes: the kernel cleans up held futexes at
  39  * thread exit time.
  40  */
  41
  42 /*
  43  * Per-lock list entry - embedded in user-space locks, somewhere close
  44  * to the futex field. (Note: user-space uses a double-linked list to
  45  * achieve O(1) list add and remove, but the kernel only needs to know
  46  * about the forward link)
  47  *
  48  * NOTE: this structure is part of the syscall ABI, and must not be
  49  * changed.
  50  */
  51 struct robust_list {
  52         struct robust_list __user *next;
  53 };
  54
  55 /*
  56  * Per-thread list head:
  57  *
  58  * NOTE: this structure is part of the syscall ABI, and must only be
  59  * changed if the change is first communicated with the glibc folks.
  60  * (When an incompatible change is done, we'll increase the structure
  61  *  size, which glibc will detect)
  62  */
  63 struct robust_list_head {
  64         /*
  65          * The head of the list. Points back to itself if empty:
  66          */
  67         struct robust_list list;
  68
  69         /*
  70          * This relative offset is set by user-space, it gives the kernel
  71          * the relative position of the futex field to examine. This way
  72          * we keep userspace flexible, to freely shape its data-structure,
  73          * without hardcoding any particular offset into the kernel:
  74          */
  75         long futex_offset;
  76
  77         /*
  78          * The death of the thread may race with userspace setting
  79          * up a lock's links. So to handle this race, userspace first
  80          * sets this field to the address of the to-be-taken lock,
  81          * then does the lock acquire, and then adds itself to the
  82          * list, and then clears this field. Hence the kernel will
  83          * always have full knowledge of all locks that the thread
  84          * _might_ have taken. We check the owner TID in any case,
  85          * so only truly owned locks will be handled.
  86          */
  87         struct robust_list __user *list_op_pending;
  88 };
  89
  90 /*
  91  * Are there any waiters for this robust futex:
  92  */
  93 #define FUTEX_WAITERS           0x80000000
  94
  95 /*
  96  * The kernel signals via this bit that a thread holding a futex
  97  * has exited without unlocking the futex. The kernel also does
  98  * a FUTEX_WAKE on such futexes, after setting the bit, to wake
  99  * up any possible waiters:
 100  */
 101 #define FUTEX_OWNER_DIED        0x40000000
 102
 103 /*
 104  * The rest of the robust-futex field is for the TID:
 105  */
 106 #define FUTEX_TID_MASK          0x3fffffff
 107
 108 /*
 109  * This limit protects against a deliberately circular list.
 110  * (Not worth introducing an rlimit for it)
 111  */
 112 #define ROBUST_LIST_LIMIT       2048
 113
 114 #ifdef __KERNEL__
 115 long do_futex(u32 __user *uaddr, int op, u32 val, union ktime *timeout,
 116               u32 __user *uaddr2, u32 val2, u32 val3);
 117
 118 extern int
 119 handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi);
 120
 121 /*
 122  * Futexes are matched on equal values of this key.
 123  * The key type depends on whether it's a shared or private mapping.
 124  * Don't rearrange members without looking at hash_futex().
 125  *
 126  * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
 127  * We use the two low order bits of offset to tell what is the kind of key :
 128  *  00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
 129  *       (no reference on an inode or mm)
 130  *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
 131  *      mapped on a file (reference on the underlying inode)
 132  *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
 133  *       (but private mapping on an mm, and reference taken on it)
 134 */
 135
 136 #define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
 137 #define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
 138
 139 union futex_key {
 140         struct {
 141                 unsigned long pgoff;
 142                 struct inode *inode;
 143                 int offset;
 144         } shared;
 145         struct {
 146                 unsigned long address;
 147                 struct mm_struct *mm;
 148                 int offset;
 149         } private;
 150         struct {
 151                 unsigned long word;
 152                 void *ptr;
 153                 int offset;
 154         } both;
 155 };
 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