| 1 | /*
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| 2 | * Copyright (c) 2012 Adam Hraska
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms, with or without
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| 6 | * modification, are permitted provided that the following conditions
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| 7 | * are met:
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| 8 | *
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| 9 | * - Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * - Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * - The name of the author may not be used to endorse or promote products
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| 15 | * derived from this software without specific prior written permission.
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| 16 | *
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | */
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| 28 |
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| 29 | /** @addtogroup libc
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| 30 | * @{
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| 31 | */
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| 32 | /**
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| 33 | * @file
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| 34 | */
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| 35 |
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| 36 | #ifndef LIBURCU_RCU_H_
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| 37 | #define LIBURCU_RCU_H_
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| 38 |
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| 39 | #include <barrier.h>
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| 40 | #include <stdbool.h>
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| 41 |
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| 42 | /** Use to assign a pointer to newly initialized data to a rcu reader
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| 43 | * accessible pointer.
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| 44 | *
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| 45 | * Example:
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| 46 | * @code
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| 47 | * typedef struct exam {
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| 48 | * struct exam *next;
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| 49 | * int grade;
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| 50 | * } exam_t;
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| 51 | *
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| 52 | * exam_t *exam_list;
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| 53 | * // ..
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| 54 | *
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| 55 | * // Insert at the beginning of the list.
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| 56 | * exam_t *my_exam = malloc(sizeof(exam_t));
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| 57 | * my_exam->grade = 5;
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| 58 | * my_exam->next = exam_list;
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| 59 | * rcu_assign(exam_list, my_exam);
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| 60 | *
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| 61 | * // Changes properly propagate. Every reader either sees
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| 62 | * // the old version of exam_list or the new version with
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| 63 | * // the fully initialized my_exam.
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| 64 | * rcu_synchronize();
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| 65 | * // Now we can be sure every reader sees my_exam.
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| 66 | *
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| 67 | * @endcode
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| 68 | */
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| 69 | #define rcu_assign(ptr, value) \
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| 70 | do { \
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| 71 | memory_barrier(); \
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| 72 | (ptr) = (value); \
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| 73 | } while (0)
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| 74 |
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| 75 | /** Use to access RCU protected data in a reader section.
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| 76 | *
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| 77 | * Example:
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| 78 | * @code
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| 79 | * exam_t *exam_list;
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| 80 | * // ...
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| 81 | *
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| 82 | * rcu_read_lock();
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| 83 | * exam_t *first_exam = rcu_access(exam_list);
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| 84 | * // We can now safely use first_exam, it won't change
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| 85 | * // under us while we're using it.
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| 86 | *
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| 87 | * // ..
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| 88 | * rcu_read_unlock();
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| 89 | * @endcode
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| 90 | */
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| 91 | #define rcu_access(ptr) ACCESS_ONCE(ptr)
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| 92 |
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| 93 | extern void rcu_register_fibril(void);
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| 94 | extern void rcu_deregister_fibril(void);
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| 95 |
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| 96 | extern void rcu_read_lock(void);
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| 97 | extern void rcu_read_unlock(void);
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| 98 |
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| 99 | extern bool rcu_read_locked(void);
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| 100 |
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| 101 | extern void rcu_synchronize(void);
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| 102 |
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| 103 | #endif
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| 104 |
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| 105 | /** @}
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| 106 | */
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