| 1 | /* |
| 2 | * Copyright (C) 2022 Jérémie Galarneau <jeremie.galarneau@efficios.com> |
| 3 | * |
| 4 | * SPDX-License-Identifier: LGPL-2.1-only |
| 5 | * |
| 6 | */ |
| 7 | |
| 8 | #ifndef LTTNG_URCU_H |
| 9 | #define LTTNG_URCU_H |
| 10 | |
| 11 | #define _LGPL_SOURCE |
| 12 | #include <mutex> |
| 13 | #include <urcu.h> |
| 14 | |
| 15 | namespace lttng { |
| 16 | namespace urcu { |
| 17 | |
| 18 | namespace details { |
| 19 | /* |
| 20 | * Wrapper around an urcu read lock which satisfies the 'Mutex' named |
| 21 | * requirements of C++11. Satisfying those requirements facilitates the use of |
| 22 | * standard concurrency support library facilities. |
| 23 | * |
| 24 | * read_lock is under the details namespace since it is unlikely to be used |
| 25 | * directly by exception-safe code. See read_lock_guard. |
| 26 | */ |
| 27 | class read_lock { |
| 28 | public: |
| 29 | read_lock() = default; |
| 30 | ~read_lock() = default; |
| 31 | |
| 32 | /* "Not copyable" and "not moveable" Mutex requirements. */ |
| 33 | read_lock(read_lock const&) = delete; |
| 34 | read_lock(read_lock&&) = delete; |
| 35 | read_lock& operator=(read_lock&&) = delete; |
| 36 | read_lock& operator=(const read_lock&) = delete; |
| 37 | |
| 38 | void lock() |
| 39 | { |
| 40 | rcu_read_lock(); |
| 41 | } |
| 42 | |
| 43 | bool try_lock() |
| 44 | { |
| 45 | lock(); |
| 46 | return true; |
| 47 | } |
| 48 | |
| 49 | void unlock() |
| 50 | { |
| 51 | rcu_read_unlock(); |
| 52 | } |
| 53 | }; |
| 54 | } /* namespace details */ |
| 55 | |
| 56 | /* |
| 57 | * Provides the basic concept of std::lock_guard for rcu reader locks. |
| 58 | * |
| 59 | * The RCU reader lock is held for the duration of lock_guard's lifetime. |
| 60 | */ |
| 61 | class read_lock_guard { |
| 62 | public: |
| 63 | read_lock_guard() = default; |
| 64 | ~read_lock_guard() = default; |
| 65 | |
| 66 | read_lock_guard(const read_lock_guard&) = delete; |
| 67 | read_lock_guard(read_lock_guard&&) = delete; |
| 68 | read_lock_guard& operator=(read_lock_guard&&) = delete; |
| 69 | read_lock_guard& operator=(const read_lock_guard&) = delete; |
| 70 | |
| 71 | private: |
| 72 | details::read_lock _lock; |
| 73 | std::lock_guard<details::read_lock> _guard{ _lock }; |
| 74 | }; |
| 75 | |
| 76 | using unique_read_lock = std::unique_lock<details::read_lock>; |
| 77 | |
| 78 | } /* namespace urcu */ |
| 79 | } /* namespace lttng */ |
| 80 | |
| 81 | #endif /* LTTNG_URCU_H */ |