18355807267

Committed 08 Oct 2025 07:27PM UTC coverage: 88.651%. First build

Build # 18355807267

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Pull #400

github

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web-flow

Commit Message

Merge 82d22144f into 749e5b474

Pull Request Pull Request #400: Executor types remove circular refs

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/include/coro/shared_mutex.hpp

#pragma once

#include "coro/concepts/executor.hpp"
#include "coro/mutex.hpp"
#include "coro/task.hpp"

#include <atomic>
#include <coroutine>

namespace coro
{
template<concepts::executor executor_type>
class shared_mutex;

namespace detail
{
template<concepts::executor executor_type>
struct shared_lock_operation
{
    explicit shared_lock_operation(coro::shared_mutex<executor_type>& shared_mutex, const bool exclusive)
        : m_shared_mutex(shared_mutex),
          m_exclusive(exclusive)
    {}
    ~shared_lock_operation() = default;

    shared_lock_operation(const shared_lock_operation&) = delete;
    shared_lock_operation(shared_lock_operation&&) = delete;
    auto operator=(const shared_lock_operation&) -> shared_lock_operation& = delete;
    auto operator=(shared_lock_operation&&) -> shared_lock_operation& = delete;

    auto await_ready() const noexcept -> bool
    {
        // If either mode can be acquired, unlock the internal mutex and resume.

        if (m_exclusive)
        {
            if (m_shared_mutex.try_lock_locked())
            {
                m_shared_mutex.m_mutex.unlock();
                return true;
            }
        }
        else if (m_shared_mutex.try_lock_shared_locked())
        {
            m_shared_mutex.m_mutex.unlock();
            return true;
        }

        return false;
    }

    auto await_suspend(std::coroutine_handle<> awaiting_coroutine) noexcept -> bool
    {
        // For sure the lock is currently held in a manner that it cannot be acquired, suspend ourself
        // at the end of the waiter list.

        auto* tail_waiter = m_shared_mutex.m_tail_waiter.load(std::memory_order::acquire);

        if (tail_waiter == nullptr)
        {
            m_shared_mutex.m_head_waiter = this;
            m_shared_mutex.m_tail_waiter = this;
        }
        else
        {
            tail_waiter->m_next = this;
            m_shared_mutex.m_tail_waiter         = this;
        }

        // If this is an exclusive lock acquire then mark it as so so that shared locks after this
        // exclusive one will also suspend so this exclusive lock doesn't get starved.
        if (m_exclusive)
        {
            ++m_shared_mutex.m_exclusive_waiters;
        }

        m_awaiting_coroutine = awaiting_coroutine;
        m_shared_mutex.m_mutex.unlock();
        return true;
    }

    auto await_resume() noexcept -> void { }

protected:
    friend class coro::shared_mutex<executor_type>;

    std::coroutine_handle<> m_awaiting_coroutine;
    shared_lock_operation* m_next{nullptr};
    coro::shared_mutex<executor_type>& m_shared_mutex;
    bool m_exclusive{false};
};

} // namespace detail

template<concepts::executor executor_type>
class shared_mutex
{
public:
    /**
     * @param e The executor for when multiple shared waiters can be woken up at the same time,
     *          each shared waiter will be scheduled to immediately run on this executor in
     *          parallel.
     */
    explicit shared_mutex(std::unique_ptr<executor_type>& e) : m_executor(e.get())
    {
        if (m_executor == nullptr)
        {
            throw std::runtime_error{"coro::shared_mutex cannot have a nullptr executor"};
        }
    }
    ~shared_mutex() = default;

    shared_mutex(const shared_mutex&)                    = delete;
    shared_mutex(shared_mutex&&)                         = delete;
    auto operator=(const shared_mutex&) -> shared_mutex& = delete;
    auto operator=(shared_mutex&&) -> shared_mutex&      = delete;

    /**
     * Acquires the lock in a shared state, executes the scoped task, and then unlocks the shared lock.
     * Because unlocking a coro::shared_mutex is a task this scoped version cannot be returned as a RAII
     * object due to destructors not being able to be co_await'ed.
     * @param scoped_task The user's scoped task to execute after acquiring the shared lock.
     */
    [[nodiscard]] auto scoped_lock_shared(coro::task<void> scoped_task) -> coro::task<void>
    {
        co_await m_mutex.lock();
        co_await detail::shared_lock_operation<executor_type>{*this, false};
        co_await scoped_task;
        co_await unlock_shared();
        co_return;
    }

    /**
     * Acquires the lock in an exclusive state, executes the scoped task, and then unlocks the exclusive lock.
     * Because unlocking a coro::shared_mutex is a task this scoped version cannot be returned as a RAII
     * object due to destructors not being able to be co_await'ed.
     * @param scoped_task The user's scoped task to execute after acquiring the exclusive lock.
     */
    [[nodiscard]] auto scoped_lock(coro::task<void> scoped_task) -> coro::task<void>
    {
        co_await m_mutex.lock();
        co_await detail::shared_lock_operation<executor_type>{*this, true};
        co_await scoped_task;
        co_await unlock();
        co_return;
    }

    /**
     * Acquires the lock in a shared state. The shared_mutex must be unlock_shared() to release.
     * @return task
     */
    [[nodiscard]] auto lock_shared() -> coro::task<void>
    {
        co_await m_mutex.lock();
        co_await detail::shared_lock_operation<executor_type>{*this, false};
        co_return;
    }

    /**
     * Acquires the lock in an exclusive state. The shared_mutex must be unlock()'ed to release.
     * @return task
     */
    [[nodiscard]] auto lock() -> coro::task<void>
    {
        co_await m_mutex.lock();
        co_await detail::shared_lock_operation<executor_type>{*this, true};
        co_return;
    }

    /**
     * @return True if the lock could immediately be acquired in a shared state.
     */
    [[nodiscard]] auto try_lock_shared() -> bool
    {
        // To acquire the shared lock the state must be one of two states:
        //   1) unlocked
        //   2) shared locked with zero exclusive waiters
        //          Zero exclusive waiters prevents exclusive starvation if shared locks are
        //          always continuously happening.

        if (m_mutex.try_lock())
        {
            coro::scoped_lock lk{m_mutex};
            return try_lock_shared_locked();
        }
        return false;
    }

    /**
     * @return True if the lock could immediately be acquired in an exclusive state.
     */
    [[nodiscard]] auto try_lock() -> bool
    {
        // To acquire the exclusive lock the state must be unlocked.
        if (m_mutex.try_lock())
        {
            coro::scoped_lock lk{m_mutex};
            return try_lock_locked();
        }
        return false;
    }

    /**
     * Unlocks a single shared state user. *REQUIRES* that the lock was first acquired exactly once
     * via `lock_shared()` or `try_lock_shared() -> True` before being called, otherwise undefined
     * behavior.
     *
     * If the shared user count drops to zero and this lock has an exclusive waiter then the exclusive
     * waiter acquires the lock.
     */
    [[nodiscard]] auto unlock_shared() -> coro::task<void>
    {
        auto lk = co_await m_mutex.scoped_lock();
        auto users = m_shared_users.fetch_sub(1, std::memory_order::acq_rel);

        // If this is the final unlock_shared() see if there is anyone to wakeup.
        if (users == 1)
        {
            auto* head_waiter = m_head_waiter.load(std::memory_order::acquire);
            if (head_waiter != nullptr)
            {
                wake_waiters(lk, head_waiter);
            }
            else
            {
                m_state = state::unlocked;
            }
        }

        co_return;
    }

    /**
     * Unlocks the mutex from its exclusive state. If there is a following exclusive waiter then
     * that exclusive waiter acquires the lock.  If there are 1 or more shared waiters then all the
     * shared waiters acquire the lock in a shared state in parallel and are resumed on the original
     * executor this shared mutex was created with.
     */
    [[nodiscard]] auto unlock() -> coro::task<void>
    {
        auto lk = co_await m_mutex.scoped_lock();
        auto* head_waiter = m_head_waiter.load(std::memory_order::acquire);
        if (head_waiter != nullptr)
        {
            wake_waiters(lk, head_waiter);
        }
        else
        {
            m_state = state::unlocked;
        }

        co_return;
    }

    /**
     * @brief Gets the executor that drives the shared mutex.
     *
     * @return executor_type>&
     * */
    [[nodiscard]] auto executor() -> executor_type&
    {
        return *m_executor;
    }

private:
    friend struct detail::shared_lock_operation<executor_type>;

    enum class state
    {
        /// @brief The shared mutex is unlocked.
        unlocked,
        /// @brief The shared mutex is locked in shared mode.
        locked_shared,
        /// @brief The shared mutex is locked in exclusive mode.
        locked_exclusive
    };

    /// @brief This executor is for resuming multiple shared waiters.
    executor_type* m_executor{nullptr};
    /// @brief Exclusive access for mutating the shared mutex's state.
    coro::mutex m_mutex;
    /// @brief The current state of the shared mutex.
    std::atomic<state> m_state{state::unlocked};

    /// @brief The current number of shared users that have acquired the lock.
    std::atomic<uint64_t> m_shared_users{0};
    /// @brief The current number of exclusive waiters waiting to acquire the lock.  This is used to block
    ///        new incoming shared lock attempts so the exclusive waiter is not starved.
    std::atomic<uint64_t> m_exclusive_waiters{0};

    std::atomic<detail::shared_lock_operation<executor_type>*> m_head_waiter{nullptr};
    std::atomic<detail::shared_lock_operation<executor_type>*> m_tail_waiter{nullptr};

    auto try_lock_shared_locked() -> bool
    {
        if (m_state == state::unlocked)
        {
            // If the shared mutex is unlocked put it into shared mode and add ourself as using the lock.
            m_state = state::locked_shared;
            ++m_shared_users;
            return true;
        }
        else if (m_state == state::locked_shared && m_exclusive_waiters == 0)
        {
            // If the shared mutex is in a shared locked state and there are no exclusive waiters
            // the add ourself as using the lock.
            ++m_shared_users;
            return true;
        }

        // If the lock is in shared mode but there are exclusive waiters then we will also wait so
        // the writers are not starved.

        // If the lock is in exclusive mode already then we need to wait.

        return false;
    }

    auto try_lock_locked() -> bool
    {
        if (m_state == state::unlocked)
        {
            m_state = state::locked_exclusive;
            return true;
        }
        return false;
    }

    auto wake_waiters(coro::scoped_lock& lk, detail::shared_lock_operation<executor_type>* head_waiter) -> void
    {
        // First determine what the next lock state will be based on the first waiter.
        if (head_waiter->m_exclusive)
        {
            // If its exclusive then only this waiter can be woken up.
            m_state.store(state::locked_exclusive, std::memory_order::release);
            if (head_waiter->m_next == nullptr)
            {
                // This is the final waiter, set the list to null.
                m_head_waiter.store(nullptr, std::memory_order::release);
                m_tail_waiter.store(nullptr, std::memory_order::release);
            }
            else
            {
                // Advance the head waiter to next.
                m_head_waiter.store(head_waiter->m_next, std::memory_order::release);
            }

            m_exclusive_waiters.fetch_sub(1, std::memory_order::release);

            // Since this is an exclusive lock waiting we can resume it directly.
            lk.unlock();
            head_waiter->m_awaiting_coroutine.resume();
        }
        else
        {
            // If its shared then we will scan forward and awake all shared waiters onto the given
            // thread pool so they can run in parallel.
            m_state.store(state::locked_shared, std::memory_order::release);
            while (true)
            {
                auto* to_resume = m_head_waiter.load(std::memory_order::acquire);
                if (to_resume == nullptr || to_resume->m_exclusive)
                {
                    break;
                }

                if (to_resume->m_next == nullptr)
                {
                    m_head_waiter.store(nullptr, std::memory_order::release);
                    m_tail_waiter.store(nullptr, std::memory_order::release);
                }
                else
                {
                    m_head_waiter.store(to_resume->m_next, std::memory_order::release);
                }

                m_shared_users.fetch_add(1, std::memory_order::release);

                m_executor->resume(to_resume->m_awaiting_coroutine);
            }

            // Cannot unlock until the entire set of shared waiters has been traversed. I think this
            // makes more sense than allocating space for all the shared waiters, unlocking, and then
            // resuming in a batch?
            lk.unlock();
        }
    }
};

} // namespace coro

1	#pragma once
2
3	#include "coro/concepts/executor.hpp"
4	#include "coro/mutex.hpp"
5	#include "coro/task.hpp"
6
7	#include <atomic>
8	#include <coroutine>
9
10	namespace coro
11	{
12	template<concepts::executor executor_type>
13	class shared_mutex;
14
15	namespace detail
16	{
17	template<concepts::executor executor_type>
18	struct shared_lock_operation
19	{
20	explicit shared_lock_operation(coro::shared_mutex<executor_type>& shared_mutex, const bool exclusive)	100✔
21	: m_shared_mutex(shared_mutex),	100✔
22	m_exclusive(exclusive)	100✔
23	{}	100✔
24	~shared_lock_operation() = default;
25
26	shared_lock_operation(const shared_lock_operation&) = delete;
27	shared_lock_operation(shared_lock_operation&&) = delete;
28	auto operator=(const shared_lock_operation&) -> shared_lock_operation& = delete;
29	auto operator=(shared_lock_operation&&) -> shared_lock_operation& = delete;
30
31	auto await_ready() const noexcept -> bool	100✔
32	{
33	// If either mode can be acquired, unlock the internal mutex and resume.
34
35	if (m_exclusive)	100✔
36	{
37	if (m_shared_mutex.try_lock_locked())	3✔
38	{
39	m_shared_mutex.m_mutex.unlock();	3✔
40	return true;	3✔
41	}
42	}
43	else if (m_shared_mutex.try_lock_shared_locked())	97✔
44	{
45	m_shared_mutex.m_mutex.unlock();	50✔
46	return true;	50✔
47	}
48
49	return false;	47✔
50	}
51
52	auto await_suspend(std::coroutine_handle<> awaiting_coroutine) noexcept -> bool	47✔
53	{
54	// For sure the lock is currently held in a manner that it cannot be acquired, suspend ourself
55	// at the end of the waiter list.
56
57	auto* tail_waiter = m_shared_mutex.m_tail_waiter.load(std::memory_order::acquire);	47✔
58
59	if (tail_waiter == nullptr)	47✔
60	{
61	m_shared_mutex.m_head_waiter = this;	1✔
62	m_shared_mutex.m_tail_waiter = this;	1✔
63	}
64	else
65	{
66	tail_waiter->m_next = this;	46✔
67	m_shared_mutex.m_tail_waiter = this;	46✔
68	}
69
70	// If this is an exclusive lock acquire then mark it as so so that shared locks after this
71	// exclusive one will also suspend so this exclusive lock doesn't get starved.
72	if (m_exclusive)	47✔
73	{
74	++m_shared_mutex.m_exclusive_waiters;	×
75	}
76
77	m_awaiting_coroutine = awaiting_coroutine;	47✔
78	m_shared_mutex.m_mutex.unlock();	47✔
79	return true;	47✔
80	}
81
82	auto await_resume() noexcept -> void { }	100✔
83
84	protected:
85	friend class coro::shared_mutex<executor_type>;
86
87	std::coroutine_handle<> m_awaiting_coroutine;
88	shared_lock_operation* m_next{nullptr};
89	coro::shared_mutex<executor_type>& m_shared_mutex;
90	bool m_exclusive{false};
91	};
92
93	} // namespace detail
94
95	template<concepts::executor executor_type>
96	class shared_mutex
97	{
98	public:
99	/**
100	* @param e The executor for when multiple shared waiters can be woken up at the same time,
101	* each shared waiter will be scheduled to immediately run on this executor in
102	* parallel.
103	*/
104	explicit shared_mutex(std::unique_ptr<executor_type>& e) : m_executor(e.get())	5✔
105	{
106	if (m_executor == nullptr)	5✔
107	{
108	throw std::runtime_error{"coro::shared_mutex cannot have a nullptr executor"};	×
109	}
110	}	5✔
111	~shared_mutex() = default;
112
113	shared_mutex(const shared_mutex&) = delete;
114	shared_mutex(shared_mutex&&) = delete;
115	auto operator=(const shared_mutex&) -> shared_mutex& = delete;
116	auto operator=(shared_mutex&&) -> shared_mutex& = delete;
117
118	/**
119	* Acquires the lock in a shared state, executes the scoped task, and then unlocks the shared lock.
120	* Because unlocking a coro::shared_mutex is a task this scoped version cannot be returned as a RAII
121	* object due to destructors not being able to be co_await'ed.
122	* @param scoped_task The user's scoped task to execute after acquiring the shared lock.
123	*/
124	[[nodiscard]] auto scoped_lock_shared(coro::task<void> scoped_task) -> coro::task<void>	1✔
125	{
126	co_await m_mutex.lock();
127	co_await detail::shared_lock_operation<executor_type>{*this, false};
128	co_await scoped_task;
129	co_await unlock_shared();
130	co_return;
131	}	2✔
132
133	/**
134	* Acquires the lock in an exclusive state, executes the scoped task, and then unlocks the exclusive lock.
135	* Because unlocking a coro::shared_mutex is a task this scoped version cannot be returned as a RAII
136	* object due to destructors not being able to be co_await'ed.
137	* @param scoped_task The user's scoped task to execute after acquiring the exclusive lock.
138	*/
139	[[nodiscard]] auto scoped_lock(coro::task<void> scoped_task) -> coro::task<void>	1✔
140	{
141	co_await m_mutex.lock();
142	co_await detail::shared_lock_operation<executor_type>{*this, true};
143	co_await scoped_task;
144	co_await unlock();
145	co_return;
146	}	2✔
147
148	/**
149	* Acquires the lock in a shared state. The shared_mutex must be unlock_shared() to release.
150	* @return task
151	*/
152	[[nodiscard]] auto lock_shared() -> coro::task<void>	96✔
153	{
154	co_await m_mutex.lock();
155	co_await detail::shared_lock_operation<executor_type>{*this, false};
156	co_return;
157	}	192✔
158
159	/**
160	* Acquires the lock in an exclusive state. The shared_mutex must be unlock()'ed to release.
161	* @return task
162	*/
163	[[nodiscard]] auto lock() -> coro::task<void>	2✔
164	{
165	co_await m_mutex.lock();
166	co_await detail::shared_lock_operation<executor_type>{*this, true};
167	co_return;
168	}	4✔
169
170	/**
171	* @return True if the lock could immediately be acquired in a shared state.
172	*/
173	[[nodiscard]] auto try_lock_shared() -> bool	6✔
174	{
175	// To acquire the shared lock the state must be one of two states:
176	// 1) unlocked
177	// 2) shared locked with zero exclusive waiters
178	// Zero exclusive waiters prevents exclusive starvation if shared locks are
179	// always continuously happening.
180
181	if (m_mutex.try_lock())	6✔
182	{
183	coro::scoped_lock lk{m_mutex};	6✔
184	return try_lock_shared_locked();	6✔
185	}	6✔
186	return false;	×
187	}
188
189	/**
190	* @return True if the lock could immediately be acquired in an exclusive state.
191	*/
192	[[nodiscard]] auto try_lock() -> bool	12✔
193	{
194	// To acquire the exclusive lock the state must be unlocked.
195	if (m_mutex.try_lock())	12✔
196	{
197	coro::scoped_lock lk{m_mutex};	12✔
198	return try_lock_locked();	12✔
199	}	12✔
200	return false;	×
201	}
202
203	/**
204	* Unlocks a single shared state user. REQUIRES that the lock was first acquired exactly once
205	* via `lock_shared()` or `try_lock_shared() -> True` before being called, otherwise undefined
206	* behavior.
207	*
208	* If the shared user count drops to zero and this lock has an exclusive waiter then the exclusive
209	* waiter acquires the lock.
210	*/
211	[[nodiscard]] auto unlock_shared() -> coro::task<void>	101✔
212	{
213	auto lk = co_await m_mutex.scoped_lock();
214	auto users = m_shared_users.fetch_sub(1, std::memory_order::acq_rel);
215
216	// If this is the final unlock_shared() see if there is anyone to wakeup.
217	if (users == 1)
218	{
219	auto* head_waiter = m_head_waiter.load(std::memory_order::acquire);
220	if (head_waiter != nullptr)
221	{
222	wake_waiters(lk, head_waiter);
223	}
224	else
225	{
226	m_state = state::unlocked;
227	}
228	}
229
230	co_return;
231	}	202✔
232
233	/**
234	* Unlocks the mutex from its exclusive state. If there is a following exclusive waiter then
235	* that exclusive waiter acquires the lock. If there are 1 or more shared waiters then all the
236	* shared waiters acquire the lock in a shared state in parallel and are resumed on the original
237	* executor this shared mutex was created with.
238	*/
239	[[nodiscard]] auto unlock() -> coro::task<void>	11✔
240	{
241	auto lk = co_await m_mutex.scoped_lock();
242	auto* head_waiter = m_head_waiter.load(std::memory_order::acquire);
243	if (head_waiter != nullptr)
244	{
245	wake_waiters(lk, head_waiter);
246	}
247	else
248	{
249	m_state = state::unlocked;
250	}
251
252	co_return;
253	}	22✔
254
255	/**
256	* @brief Gets the executor that drives the shared mutex.
257	*
258	* @return executor_type>&
259	* */
NEW 260	[[nodiscard]] auto executor() -> executor_type&	×
261	{
NEW 262	return *m_executor;	×
263	}
264
265	private:
266	friend struct detail::shared_lock_operation<executor_type>;
267
268	enum class state
269	{
270	/// @brief The shared mutex is unlocked.
271	unlocked,
272	/// @brief The shared mutex is locked in shared mode.
273	locked_shared,
274	/// @brief The shared mutex is locked in exclusive mode.
275	locked_exclusive
276	};
277
278	/// @brief This executor is for resuming multiple shared waiters.
279	executor_type* m_executor{nullptr};
280	/// @brief Exclusive access for mutating the shared mutex's state.
281	coro::mutex m_mutex;
282	/// @brief The current state of the shared mutex.
283	std::atomic<state> m_state{state::unlocked};
284
285	/// @brief The current number of shared users that have acquired the lock.
286	std::atomic<uint64_t> m_shared_users{0};
287	/// @brief The current number of exclusive waiters waiting to acquire the lock. This is used to block
288	/// new incoming shared lock attempts so the exclusive waiter is not starved.
289	std::atomic<uint64_t> m_exclusive_waiters{0};
290
291	std::atomic<detail::shared_lock_operation<executor_type>*> m_head_waiter{nullptr};
292	std::atomic<detail::shared_lock_operation<executor_type>*> m_tail_waiter{nullptr};
293
294	auto try_lock_shared_locked() -> bool	103✔
295	{
296	if (m_state == state::unlocked)	103✔
297	{
298	// If the shared mutex is unlocked put it into shared mode and add ourself as using the lock.
299	m_state = state::locked_shared;	52✔
300	++m_shared_users;	52✔
301	return true;	52✔
302	}
303	else if (m_state == state::locked_shared && m_exclusive_waiters == 0)	51✔
304	{
305	// If the shared mutex is in a shared locked state and there are no exclusive waiters
306	// the add ourself as using the lock.
307	++m_shared_users;	2✔
308	return true;	2✔
309	}
310
311	// If the lock is in shared mode but there are exclusive waiters then we will also wait so
312	// the writers are not starved.
313
314	// If the lock is in exclusive mode already then we need to wait.
315
316	return false;	49✔
317	}
318
319	auto try_lock_locked() -> bool	15✔
320	{
321	if (m_state == state::unlocked)	15✔
322	{
323	m_state = state::locked_exclusive;	11✔
324	return true;	11✔
325	}
326	return false;	4✔
327	}
328
329	auto wake_waiters(coro::scoped_lock& lk, detail::shared_lock_operation<executor_type>* head_waiter) -> void	1✔
330	{
331	// First determine what the next lock state will be based on the first waiter.
332	if (head_waiter->m_exclusive)	1✔
333	{
334	// If its exclusive then only this waiter can be woken up.
335	m_state.store(state::locked_exclusive, std::memory_order::release);	×
336	if (head_waiter->m_next == nullptr)	×
337	{
338	// This is the final waiter, set the list to null.
339	m_head_waiter.store(nullptr, std::memory_order::release);	×
340	m_tail_waiter.store(nullptr, std::memory_order::release);	×
341	}
342	else
343	{
344	// Advance the head waiter to next.
345	m_head_waiter.store(head_waiter->m_next, std::memory_order::release);	×
346	}
347
348	m_exclusive_waiters.fetch_sub(1, std::memory_order::release);	×
349
350	// Since this is an exclusive lock waiting we can resume it directly.
351	lk.unlock();	×
352	head_waiter->m_awaiting_coroutine.resume();	×
353	}
354	else
355	{
356	// If its shared then we will scan forward and awake all shared waiters onto the given
357	// thread pool so they can run in parallel.
358	m_state.store(state::locked_shared, std::memory_order::release);	1✔
359	while (true)	47✔
360	{
361	auto* to_resume = m_head_waiter.load(std::memory_order::acquire);	48✔
362	if (to_resume == nullptr \|\| to_resume->m_exclusive)	48✔
363	{
364	break;
365	}
366
367	if (to_resume->m_next == nullptr)	47✔
368	{
369	m_head_waiter.store(nullptr, std::memory_order::release);	1✔
370	m_tail_waiter.store(nullptr, std::memory_order::release);	1✔
371	}
372	else
373	{
374	m_head_waiter.store(to_resume->m_next, std::memory_order::release);	46✔
375	}
376
377	m_shared_users.fetch_add(1, std::memory_order::release);	47✔
378
379	m_executor->resume(to_resume->m_awaiting_coroutine);	47✔
380	}
381
382	// Cannot unlock until the entire set of shared waiters has been traversed. I think this
383	// makes more sense than allocating space for all the shared waiters, unlocking, and then
384	// resuming in a batch?
385	lk.unlock();	1✔
386	}
387	}	1✔
388	};
389
390	} // namespace coro

jbaldwin / libcoro / 18355807267

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