forked from suyu/suyu
polyfill_thread: satisfy execution ordering requirements of stop_callback
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2efe42fc93
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619c0e70f0
1 changed files with 48 additions and 39 deletions
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@ -41,17 +41,18 @@ bool StoppableTimedWait(std::stop_token token, const std::chrono::duration<Rep,
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#include <chrono>
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#include <condition_variable>
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#include <functional>
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#include <list>
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#include <map>
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#include <memory>
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#include <mutex>
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#include <optional>
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#include <thread>
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#include <type_traits>
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#include <utility>
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namespace std {
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namespace polyfill {
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using stop_state_callbacks = list<function<void()>>;
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using stop_state_callback = size_t;
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class stop_state {
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public:
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@ -59,61 +60,69 @@ public:
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~stop_state() = default;
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bool request_stop() {
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stop_state_callbacks callbacks;
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unique_lock lk{m_lock};
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{
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scoped_lock lk{m_lock};
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if (m_stop_requested.load()) {
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// Already set, nothing to do
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if (m_stop_requested) {
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// Already set, nothing to do.
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return false;
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}
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// Set as requested
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// Mark stop requested.
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m_stop_requested = true;
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// Copy callback list
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callbacks = m_callbacks;
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}
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while (!m_callbacks.empty()) {
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// Get an iterator to the first element.
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const auto it = m_callbacks.begin();
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for (auto callback : callbacks) {
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callback();
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// Move the callback function out of the map.
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function<void()> f;
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swap(it->second, f);
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// Erase the now-empty map element.
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m_callbacks.erase(it);
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// Run the callback.
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if (f) {
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f();
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}
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}
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return true;
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}
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bool stop_requested() const {
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return m_stop_requested.load();
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unique_lock lk{m_lock};
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return m_stop_requested;
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}
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stop_state_callbacks::const_iterator insert_callback(function<void()> f) {
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stop_state_callbacks::const_iterator ret{};
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bool should_run{};
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stop_state_callback insert_callback(function<void()> f) {
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unique_lock lk{m_lock};
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{
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scoped_lock lk{m_lock};
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should_run = m_stop_requested.load();
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m_callbacks.push_front(f);
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ret = m_callbacks.begin();
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}
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if (should_run) {
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if (m_stop_requested) {
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// Stop already requested. Don't insert anything,
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// just run the callback synchronously.
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if (f) {
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f();
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}
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return 0;
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}
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// Insert the callback.
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stop_state_callback ret = ++m_next_callback;
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m_callbacks.emplace(ret, move(f));
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return ret;
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}
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void remove_callback(stop_state_callbacks::const_iterator it) {
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scoped_lock lk{m_lock};
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m_callbacks.erase(it);
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void remove_callback(stop_state_callback cb) {
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unique_lock lk{m_lock};
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m_callbacks.erase(cb);
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}
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private:
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mutex m_lock;
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atomic<bool> m_stop_requested;
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stop_state_callbacks m_callbacks;
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mutable recursive_mutex m_lock;
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map<stop_state_callback, function<void()>> m_callbacks;
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stop_state_callback m_next_callback{0};
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bool m_stop_requested{false};
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};
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} // namespace polyfill
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@ -223,7 +232,7 @@ public:
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}
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~stop_callback() {
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if (m_stop_state && m_callback) {
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m_stop_state->remove_callback(*m_callback);
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m_stop_state->remove_callback(m_callback);
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}
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}
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@ -234,7 +243,7 @@ public:
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private:
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shared_ptr<polyfill::stop_state> m_stop_state;
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optional<polyfill::stop_state_callbacks::const_iterator> m_callback;
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polyfill::stop_state_callback m_callback;
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};
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template <typename Callback>
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