/usr/include/urcu/static/urcu-pointer.h is in liburcu-dev 0.9.1-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 | #ifndef _URCU_POINTER_STATIC_H
#define _URCU_POINTER_STATIC_H
/*
* urcu-pointer-static.h
*
* Userspace RCU header. Operations on pointers.
*
* TO BE INCLUDED ONLY IN CODE THAT IS TO BE RECOMPILED ON EACH LIBURCU
* RELEASE. See urcu.h for linking dynamically with the userspace rcu library.
*
* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
#include <urcu/compiler.h>
#include <urcu/arch.h>
#include <urcu/system.h>
#include <urcu/uatomic.h>
#ifdef __cplusplus
extern "C" {
#endif
/**
* _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable
* into a RCU read-side critical section. The pointer can later be safely
* dereferenced within the critical section.
*
* This ensures that the pointer copy is invariant thorough the whole critical
* section.
*
* Inserts memory barriers on architectures that require them (currently only
* Alpha) and documents which pointers are protected by RCU.
*
* The compiler memory barrier in CMM_LOAD_SHARED() ensures that value-speculative
* optimizations (e.g. VSS: Value Speculation Scheduling) does not perform the
* data read before the pointer read by speculating the value of the pointer.
* Correct ordering is ensured because the pointer is read as a volatile access.
* This acts as a global side-effect operation, which forbids reordering of
* dependent memory operations. Note that such concern about dependency-breaking
* optimizations will eventually be taken care of by the "memory_order_consume"
* addition to forthcoming C++ standard.
*
* Should match rcu_assign_pointer() or rcu_xchg_pointer().
*
* This macro is less than 10 lines long. The intent is that this macro
* meets the 10-line criterion in LGPL, allowing this function to be
* expanded directly in non-LGPL code.
*/
#define _rcu_dereference(p) \
__extension__ \
({ \
__typeof__(p) _________p1 = CMM_LOAD_SHARED(p); \
cmm_smp_read_barrier_depends(); \
(_________p1); \
})
/**
* _rcu_cmpxchg_pointer - same as rcu_assign_pointer, but tests if the pointer
* is as expected by "old". If succeeds, returns the previous pointer to the
* data structure, which can be safely freed after waiting for a quiescent state
* using synchronize_rcu(). If fails (unexpected value), returns old (which
* should not be freed !).
*
* This macro is less than 10 lines long. The intent is that this macro
* meets the 10-line criterion in LGPL, allowing this function to be
* expanded directly in non-LGPL code.
*/
#define _rcu_cmpxchg_pointer(p, old, _new) \
__extension__ \
({ \
__typeof__(*p) _________pold = (old); \
__typeof__(*p) _________pnew = (_new); \
if (!__builtin_constant_p(_new) || \
((_new) != NULL)) \
cmm_wmb(); \
uatomic_cmpxchg(p, _________pold, _________pnew); \
})
/**
* _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous
* pointer to the data structure, which can be safely freed after waiting for a
* quiescent state using synchronize_rcu().
*
* This macro is less than 10 lines long. The intent is that this macro
* meets the 10-line criterion in LGPL, allowing this function to be
* expanded directly in non-LGPL code.
*/
#define _rcu_xchg_pointer(p, v) \
__extension__ \
({ \
__typeof__(*p) _________pv = (v); \
if (!__builtin_constant_p(v) || \
((v) != NULL)) \
cmm_wmb(); \
uatomic_xchg(p, _________pv); \
})
#define _rcu_set_pointer(p, v) \
do { \
__typeof__(*p) _________pv = (v); \
if (!__builtin_constant_p(v) || \
((v) != NULL)) \
cmm_wmb(); \
uatomic_set(p, _________pv); \
} while (0)
/**
* _rcu_assign_pointer - assign (publicize) a pointer to a new data structure
* meant to be read by RCU read-side critical sections. Returns the assigned
* value.
*
* Documents which pointers will be dereferenced by RCU read-side critical
* sections and adds the required memory barriers on architectures requiring
* them. It also makes sure the compiler does not reorder code initializing the
* data structure before its publication.
*
* Should match rcu_dereference().
*
* This macro is less than 10 lines long. The intent is that this macro
* meets the 10-line criterion in LGPL, allowing this function to be
* expanded directly in non-LGPL code.
*/
#define _rcu_assign_pointer(p, v) _rcu_set_pointer(&(p), v)
#ifdef __cplusplus
}
#endif
#endif /* _URCU_POINTER_STATIC_H */
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