include/lttng/urcu/pointer.h

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