include/linux/futex.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_FUTEX_H
   3 #define _LINUX_FUTEX_H
   4
   5 #include <linux/sched.h>
   6 #include <linux/ktime.h>
   7
   8 #include <uapi/linux/futex.h>
   9
  10 struct inode;
  11 struct mm_struct;
  12 struct task_struct;
  13
  14 /*
  15  * Futexes are matched on equal values of this key.
  16  * The key type depends on whether it's a shared or private mapping.
  17  * Don't rearrange members without looking at hash_futex().
  18  *
  19  * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
  20  * We use the two low order bits of offset to tell what is the kind of key :
  21  *  00 : Private process futex (PTHREAD_PROCESS_PRIVATE)
  22  *       (no reference on an inode or mm)
  23  *  01 : Shared futex (PTHREAD_PROCESS_SHARED)
  24  *      mapped on a file (reference on the underlying inode)
  25  *  10 : Shared futex (PTHREAD_PROCESS_SHARED)
  26  *       (but private mapping on an mm, and reference taken on it)
  27 */
  28
  29 #define FUT_OFF_INODE    1 /* We set bit 0 if key has a reference on inode */
  30 #define FUT_OFF_MMSHARED 2 /* We set bit 1 if key has a reference on mm */
  31
  32 union futex_key {
  33         struct {
  34                 unsigned long pgoff;
  35                 struct inode *inode;
  36                 int offset;
  37         } shared;
  38         struct {
  39                 unsigned long address;
  40                 struct mm_struct *mm;
  41                 int offset;
  42         } private;
  43         struct {
  44                 unsigned long word;
  45                 void *ptr;
  46                 int offset;
  47         } both;
  48 };
  49
  50 #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
  51
  52 #ifdef CONFIG_FUTEX
  53 enum {
  54         FUTEX_STATE_OK,
  55         FUTEX_STATE_EXITING,
  56         FUTEX_STATE_DEAD,
  57 };
  58
  59 static inline void futex_init_task(struct task_struct *tsk)
  60 {
  61         tsk->robust_list = NULL;
  62 #ifdef CONFIG_COMPAT
  63         tsk->compat_robust_list = NULL;
  64 #endif
  65         INIT_LIST_HEAD(&tsk->pi_state_list);
  66         tsk->pi_state_cache = NULL;
  67         tsk->futex_state = FUTEX_STATE_OK;
  68         mutex_init(&tsk->futex_exit_mutex);
  69 }
  70
  71 void futex_exit_recursive(struct task_struct *tsk);
  72 void futex_exit_release(struct task_struct *tsk);
  73 void futex_exec_release(struct task_struct *tsk);
  74
  75 long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
  76               u32 __user *uaddr2, u32 val2, u32 val3);
  77 #else
  78 static inline void futex_init_task(struct task_struct *tsk) { }
  79 static inline void futex_exit_recursive(struct task_struct *tsk) { }
  80 static inline void futex_exit_release(struct task_struct *tsk) { }
  81 static inline void futex_exec_release(struct task_struct *tsk) { }
  82 static inline long do_futex(u32 __user *uaddr, int op, u32 val,
  83                             ktime_t *timeout, u32 __user *uaddr2,
  84                             u32 val2, u32 val3)
  85 {
  86         return -EINVAL;
  87 }
  88 #endif
  89
  90 #endif