Jbaldwin/condvar lost wake task group #419
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To avoid lost wakeups, use an internal mutex to protect modification of the awaiter list. Now, while we are notifying, if another notification task arrives it must wait for our modification of the awaiter list to complete. Hence waiters that were not ready and are pushed back on the list have a chance to be woken up by the next notification. - Closes #398
jbaldwin
commented
Nov 26, 2025
include/coro/condition_variable.hpp
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| waiter = waiter->m_next; | ||
| } | ||
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| coro::task_group group{executor, std::move(notify_tasks)}; |
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I think this could possibly also just be a when_all(notify_tasks) but we'd need to refactor how make_notify_all_executor_individual_task() work internally to possibly take an executor and if it receives one to schedule itself.. which honestly is probably more efficient since it won't introduce the task_self_deleting as an intermediate, just a schedule co_await.
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updated with another patchset to show when_all usage, I think they are roughly equivalent, but when_all seems a little more appropriate since we actually do know the lifetime of the tasks, and task_group should be use for more dynamic lifetimes
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