| 1 | /* |
| 2 | * Copyright (C) 2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 3 | * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com> |
| 4 | * |
| 5 | * SPDX-License-Identifier: LGPL-2.1-only |
| 6 | * |
| 7 | * This code is originally adapted from userspace-rcu's urcu-wait.h |
| 8 | */ |
| 9 | |
| 10 | #ifndef LTTNG_WAITER_H |
| 11 | #define LTTNG_WAITER_H |
| 12 | |
| 13 | #define _LGPL_SOURCE |
| 14 | |
| 15 | #include "macros.hpp" |
| 16 | |
| 17 | #include <stdbool.h> |
| 18 | #include <stdint.h> |
| 19 | #include <urcu/wfstack.h> |
| 20 | |
| 21 | namespace lttng { |
| 22 | namespace synchro { |
| 23 | class waiter; |
| 24 | class wait_queue; |
| 25 | |
| 26 | class waker { |
| 27 | friend waiter; |
| 28 | |
| 29 | public: |
| 30 | waker(const waker&) = default; |
| 31 | waker(waker&&) = default; |
| 32 | waker& operator=(const waker& other) |
| 33 | { |
| 34 | _state = other._state; |
| 35 | return *this; |
| 36 | } |
| 37 | waker& operator=(waker&& other) |
| 38 | { |
| 39 | _state = other._state; |
| 40 | return *this; |
| 41 | } |
| 42 | |
| 43 | void wake(); |
| 44 | |
| 45 | ~waker() = default; |
| 46 | |
| 47 | private: |
| 48 | waker(int32_t& state) : _state{ state } |
| 49 | { |
| 50 | } |
| 51 | |
| 52 | int32_t& _state; |
| 53 | }; |
| 54 | |
| 55 | class waiter final { |
| 56 | friend wait_queue; |
| 57 | |
| 58 | public: |
| 59 | waiter(); |
| 60 | |
| 61 | /* Deactivate copy and assignment. */ |
| 62 | waiter(const waiter&) = delete; |
| 63 | waiter(waiter&&) = delete; |
| 64 | waiter& operator=(const waiter&) = delete; |
| 65 | waiter& operator=(waiter&&) = delete; |
| 66 | ~waiter() = default; |
| 67 | |
| 68 | void arm() noexcept; |
| 69 | void wait(); |
| 70 | |
| 71 | waker get_waker(); |
| 72 | |
| 73 | private: |
| 74 | cds_wfs_node _wait_queue_node; |
| 75 | int32_t _state; |
| 76 | }; |
| 77 | |
| 78 | class wait_queue final { |
| 79 | public: |
| 80 | wait_queue(); |
| 81 | |
| 82 | /* Deactivate copy and assignment. */ |
| 83 | wait_queue(const wait_queue&) = delete; |
| 84 | wait_queue(wait_queue&&) = delete; |
| 85 | wait_queue& operator=(const wait_queue&) = delete; |
| 86 | wait_queue& operator=(wait_queue&&) = delete; |
| 87 | ~wait_queue() = default; |
| 88 | |
| 89 | /* |
| 90 | * Atomically add a waiter to a wait queue. |
| 91 | * A full memory barrier is issued before being added to the wait queue. |
| 92 | */ |
| 93 | void add(waiter& waiter) noexcept; |
| 94 | /* |
| 95 | * Wake every waiter present in the wait queue and remove them from |
| 96 | * the queue. |
| 97 | */ |
| 98 | void wake_all(); |
| 99 | |
| 100 | private: |
| 101 | cds_wfs_stack _stack; |
| 102 | }; |
| 103 | } /* namespace synchro */ |
| 104 | } /* namespace lttng */ |
| 105 | |
| 106 | #endif /* LTTNG_WAITER_H */ |