include/urcu/pointer.h

   1 // SPDX-FileCopyrightText: 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   2 // SPDX-FileCopyrightText: 2009 Paul E. McKenney, IBM Corporation.
   3 //
   4 // SPDX-License-Identifier: LGPL-2.1-or-later
   5
   6 #ifndef _URCU_POINTER_H
   7 #define _URCU_POINTER_H
   8
   9 /*
  10  * Userspace RCU header. Operations on pointers.
  11  *
  12  * IBM's contributions to this file may be relicensed under LGPLv2 or later.
  13  */
  14
  15 #include <urcu/compiler.h>
  16 #include <urcu/arch.h>
  17 #include <urcu/uatomic.h>
  18
  19 #ifdef __cplusplus
  20 extern "C" {
  21 #endif
  22
  23 #if defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)
  24
  25 #include <urcu/static/pointer.h>
  26
  27 /*
  28  * rcu_dereference(ptr)
  29  *
  30  * Fetch a RCU-protected pointer. Typically used to copy the variable ptr to a
  31  * local variable.
  32  */
  33 #define rcu_dereference         _rcu_dereference
  34
  35 /*
  36  * type *rcu_cmpxchg_pointer(type **ptr, type *new, type *old)
  37  * type *rcu_xchg_pointer(type **ptr, type *new)
  38  * void rcu_set_pointer(type **ptr, type *new)
  39  *
  40  * RCU pointer updates.
  41  * @ptr: address of the pointer to modify
  42  * @new: new pointer value
  43  * @old: old pointer value (expected)
  44  *
  45  * return: old pointer value
  46  */
  47 #define rcu_cmpxchg_pointer     _rcu_cmpxchg_pointer
  48 #define rcu_xchg_pointer        _rcu_xchg_pointer
  49 #define rcu_set_pointer         _rcu_set_pointer
  50
  51 #else /* !(defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)) */
  52
  53 extern void *rcu_dereference_sym(void *p);
  54 #define rcu_dereference(p)                                                   \
  55         __extension__                                                        \
  56         ({                                                                   \
  57                 __typeof__(p) _________p1 =     URCU_FORCE_CAST(__typeof__(p), \
  58                         rcu_dereference_sym(URCU_FORCE_CAST(void *, p)));    \
  59                 (_________p1);                                               \
  60         })
  61
  62 extern void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new);
  63 #define rcu_cmpxchg_pointer(p, old, _new)                                    \
  64         __extension__                                                        \
  65         ({                                                                   \
  66                 __typeof__(*(p)) _________pold = (old);                      \
  67                 __typeof__(*(p)) _________pnew = (_new);                     \
  68                 __typeof__(*(p)) _________p1 = URCU_FORCE_CAST(__typeof__(*(p)), \
  69                         rcu_cmpxchg_pointer_sym(URCU_FORCE_CAST(void **, p), \
  70                                                 _________pold,               \
  71                                                 _________pnew));             \
  72                 (_________p1);                                               \
  73         })
  74
  75 extern void *rcu_xchg_pointer_sym(void **p, void *v);
  76 #define rcu_xchg_pointer(p, v)                                               \
  77         __extension__                                                        \
  78         ({                                                                   \
  79                 __typeof__(*(p)) _________pv = (v);                          \
  80                 __typeof__(*(p)) _________p1 = URCU_FORCE_CAST(__typeof__(*(p)), \
  81                         rcu_xchg_pointer_sym(URCU_FORCE_CAST(void **, p),    \
  82                                              _________pv));                  \
  83                 (_________p1);                                               \
  84         })
  85
  86 /*
  87  * Note: rcu_set_pointer_sym returns @v because we don't want to break
  88  * the ABI. At the API level, rcu_set_pointer() now returns void. Use of
  89  * the return value is therefore deprecated, and will cause a build
  90  * error.
  91  */
  92 extern void *rcu_set_pointer_sym(void **p, void *v);
  93 #define rcu_set_pointer(p, v)                                                \
  94         do {                                                                 \
  95                 __typeof__(*(p)) _________pv = (v);                          \
  96                 (void) rcu_set_pointer_sym(URCU_FORCE_CAST(void **, p),      \
  97                                             _________pv);                    \
  98         } while (0)
  99
 100 #endif /* !(defined(_LGPL_SOURCE) || defined(URCU_INLINE_SMALL_FUNCTIONS)) */
 101
 102 /*
 103  * void rcu_assign_pointer(type *ptr, type *new)
 104  *
 105  * Same as rcu_set_pointer, but takes the pointer to assign to rather than its
 106  * address as first parameter. Provided for compatibility with the Linux kernel
 107  * RCU semantic.
 108  */
 109 #define rcu_assign_pointer(p, v)        rcu_set_pointer((&p), (v))
 110
 111 #ifdef __cplusplus
 112 }
 113 #endif
 114
 115 #endif /* _URCU_POINTER_H */