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switch_to.hh
1/*
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9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
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18/*
19 * Copyright (C) 2022-present ScyllaDB
20 */
21
22#pragma once
23
24#include <seastar/core/coroutine.hh>
26
27namespace seastar::coroutine {
28
54
55struct [[nodiscard("must co_await a switch_to object")]] switch_to final : task {
56 scheduling_group _prev_sg;
57 scheduling_group _switch_to_sg;
58 task* _task = nullptr;
59public:
60 explicit switch_to(scheduling_group new_sg) noexcept
61 : _prev_sg(current_scheduling_group())
62 , _switch_to_sg(std::move(new_sg))
63 { }
64
65 switch_to(const switch_to&) = delete;
66 switch_to(switch_to&&) = delete;
67
68 bool await_ready() const noexcept {
69 return current_scheduling_group() == _switch_to_sg;
70 }
71
72 template<typename T>
73 void await_suspend(std::coroutine_handle<T> hndl) noexcept {
74 auto& t = hndl.promise();
75 t.set_scheduling_group(_switch_to_sg);
76 _task = &t;
77 schedule(_task);
78 }
79
80 scheduling_group await_resume() {
81 return _prev_sg;
82 }
83
84 virtual void run_and_dispose() noexcept override { }
85
86 virtual task* waiting_task() noexcept override {
87 return _task;
88 }
89};
90
91} // namespace seastar::coroutine
Identifies function calls that are accounted as a group.
Definition: scheduling.hh:285
Definition: task.hh:34
scheduling_group current_scheduling_group() noexcept
Returns the current scheduling group.
Definition: scheduling.hh:397
Definition: switch_to.hh:55
virtual task * waiting_task() noexcept override
Returns the next task which is waiting for this task to complete execution, or nullptr.
Definition: switch_to.hh:86